Electrosurgical instrument employing an electrode

ABSTRACT

An electrosurgical surgical instrument can comprise a handle and an end effector, wherein the end effector can comprise first and second jaws which can be opened and closed in order to capture tissue therebetween. In various embodiments, the first and second jaws can comprise one or more electrodes configured to apply a voltage across the tissue, wherein at least one of the electrodes can comprise a conductive material positioned within a non-conductive, or high-resistance, material. In use, current flowing through the conductive material can heat the conductive material and cause it to evaporate and leave behind the non-conductive material. In such circumstances, the current flowing through the electrode may cease or may be substantially reduced.

BACKGROUND

1. Field of the Invention

The present invention relates to medical devices and methods. Moreparticularly, the present invention relates to electrosurgicalinstruments and methods for sealing and transecting tissue.

2. Description of the Related Art

In various open, endoscopic, and/or laparoscopic surgeries, for example,it may be necessary to coagulate, seal, and/or fuse tissue. One means ofsealing tissue relies upon the application of electrical energy totissue captured within an end effector of a surgical instrument in orderto cause thermal effects within the tissue. Various mono-polar andbi-polar radio frequency (Rf) surgical instruments and surgicaltechniques have been developed for such purposes. In general, thedelivery of Rf energy to the captured tissue elevates the temperature ofthe tissue and, as a result, the energy can at least partially denatureproteins within the tissue. Such proteins, such as collagen, forexample, may be denatured into a proteinaceous amalgam that intermixesand fuses, or “welds”, together as the proteins renature. As the treatedregion heals over time, this biological “weld” may be reabsorbed by thebody's wound healing process.

In certain arrangements of a bi-polar radiofrequency (Rf) surgicalinstrument, the surgical instrument can comprise opposing first andsecond jaws, wherein the face of each jaw can comprise an electrode. Inuse, the tissue can be captured between the jaw faces such thatelectrical current can flow between the electrodes in the opposing jawsand through the tissue positioned therebetween. Such instruments mayhave to seal or “weld” many types of tissues, such as anatomicstructures having walls with irregular or thick fibrous content, bundlesof disparate anatomic structures, substantially thick anatomicstructures, and/or tissues with thick fascia layers such as largediameter blood vessels, for example. With particular regard to sealinglarge diameter blood vessels, for example, such applications may requirea high strength tissue weld immediately post-treatment.

The foregoing discussion is intended only to illustrate various aspectsof the related art in the field of the invention at the time, and shouldnot be taken as a disavowal of claim scope.

SUMMARY

In at least one form, a surgical instrument can comprise a handle, afirst conductor, a second conductor, and an end effector comprising afirst jaw and a second jaw, wherein one of the first jaw and the secondjaw is movable relative to the other of the first jaw and the second jawbetween an open position and a closed position. The end effector canfurther comprise a first electrode electrically coupled with the firstconductor, and a second electrode electrically coupled with the secondconductor, the second electrode comprising a porous material, and anevaporable material stored within the porous material.

In at least one form, a surgical instrument can comprise a handle, afirst conductor, a second conductor electrically engageable with a powersource, and an end effector comprising a first jaw and a second jaw,wherein one of the first jaw and the second jaw is movable relative tothe other of the first jaw and the second jaw between an open positionand a closed position. The end effector can further comprise a firstelectrode electrically coupled with the first conductor, and a secondelectrode electrically coupled with the second conductor, wherein thesecond electrode comprises a first material comprised of an electricallynon-conductive material and a second material comprised of anelectrically conductive material, and wherein the second material isinterdispersed within the first material when the second electrode isbelow a switching temperature. The second material is configured towithdraw from the first material when the temperature of the secondmaterial at least one of meets or exceeds the switching temperature.

In at least one form, an end effector for use with a surgical instrumentcan comprise a first conductor, a second conductor, a first jaw, and asecond jaw, wherein one of the first jaw and the second jaw is movablerelative to the other of the first jaw and the second jaw between anopen position and a closed position. The end effector can furthercomprise a first electrode electrically coupled with the first conductorand a second electrode electrically coupled with the second conductor,the second electrode comprising a porous material and an evaporablematerial stored within the porous material.

In at least one form, a surgical instrument can comprise a first jawcomprising an electrode, a second jaw, and a control circuit, whereinthe control circuit can comprise a supply conductor configured to beplaced in electrical communication with a positive terminal of a powersource, a temperature sensor, and a field effect transistor. The fieldeffect transistor can comprise a source terminal in electricalcommunication with the supply conductor, a drain terminal in electricalcommunication with the electrode, a gate terminal in electricalcommunication with the temperature sensor, and a channel comprising asemiconductor material in electrical communication with the sourceterminal and the drain terminal.

In at least one form, a surgical instrument can comprise a handle, afirst conductor, a second conductor, and an end effector. The endeffector can comprise a first jaw, a second jaw, wherein the first jawis movable relative to the second jaw in order to capture tissueintermediate the first jaw and the second jaw, a first electrodeelectrically coupled with the first conductor, and a second electrodeelectrically coupled with the second conductor, wherein the secondelectrode is comprised of a material configured to conduct a firstcurrent when a first pressure is applied to the material, and whereinthe material is configured to conduct a second current when a secondpressure is applied to the material.

In various embodiments, the material can comprise a substrate materialand a conductive material interdispersed within the substrate materialin a first volumetric density when the first pressure is being appliedto the material and a second volumetric density when the second pressureis being applied to the material, and wherein the second volumetricdensity is greater than the first volumetric density. In certainembodiments, the second electrode can further comprise a positivetemperature coefficient (PTC) material having a switching temperature,wherein the PTC material comprises a first electrical resistance at afirst temperature below the switching temperature and a secondelectrical resistance at a second temperature above the switchingtemperature, and wherein the second resistance is sufficient to inhibitthe conduction of electrical current therethrough.

In at least one form, a surgical instrument can comprise a handle, afirst conductor, a second conductor, and an end effector. The endeffector can comprise a first jaw, a second jaw, wherein the first jawis movable relative to the second jaw in order to capture tissueintermediate the first jaw and the second jaw, a first electrodeelectrically coupled with the first conductor, and a second electrodeelectrically coupled with the second conductor, wherein the secondelectrode is comprised of a material configured to conduct a firstcurrent when a first pressure is applied to the material, and whereinthe material is configured to inhibit current from flowing through thematerial when a second pressure is applied to the material.

In at least one form, a surgical instrument can comprise a handle, afirst conductor, a second conductor, and an end effector. The endeffector can comprise a first jaw, a second jaw, wherein the first jawis movable relative to the second jaw in order to capture tissueintermediate the first jaw and the second jaw, a first electrodeelectrically coupled with the first conductor, and a second electrodeelectrically coupled with the second conductor, wherein the secondelectrode is comprised of a material configured to have a firstelectrical resistance when a first pressure is applied to the material,and wherein the material is configured to have a second electricalresistance when a second pressure is applied to the material.

In at least one form, a surgical instrument can comprise a handle and anend effector, wherein the end effector can comprise a first jaw and asecond jaw, and wherein the first jaw is movable relative to the secondjaw between an open position and a closed position. The end effector canfurther comprise a first electrode comprised of a first positivetemperature coefficient material having a first electrical resistancewhen the temperature of the first electrode is below a first switchingtemperature and a second electrical resistance when the temperature ofthe first electrode is above the first switching temperature. The endeffector can further comprise a second electrode comprised of a secondpositive temperature coefficient material having a first electricalresistance when the temperature of the second electrode is below asecond switching temperature and a second electrical resistance when thetemperature of the second electrode is above the second switchingtemperature, wherein the second switching temperature is higher than thefirst switching temperature.

In at least one form, a surgical instrument can comprise a handle and anend effector, wherein the end effector can comprise a first jaw and asecond jaw, and wherein the first jaw is movable relative to the secondjaw. The end effector can further comprise a first electrode comprisedof a first positive temperature coefficient material having a firstelectrical resistance when the temperature of said first electrode isbelow a first switching temperature and a second electrical resistanceat least one order of magnitude higher than said first resistance whenthe temperature of the first electrode is above the first switchingtemperature. The end effector can further comprise a second electrodecomprised of a second positive temperature coefficient material having athird electrical resistance when the temperature of the second electrodeis below a second switching temperature and a fourth electricalresistance at least one order of magnitude higher than the thirdelectrical resistance when the temperature of the second electrode isabove the second switching temperature, wherein the second switchingtemperature is higher than the first switching temperature.

In at least one form, a surgical instrument can comprise a handle and anend effector, wherein the end effector can comprise a first jawcomprising a first frame having a first outer perimeter and a firstelectrode positioned within the first frame. The end effector canfurther comprise a second jaw, wherein one of the first jaw and thesecond jaw is movable relative to the other of the first jaw and thesecond jaw between an open position and a closed position, the secondjaw comprising a second frame having a second outer perimeter and asecond electrode positioned within said second frame. At least one ofthe first outer perimeter and the second outer perimeter is comprised ofa positive temperature coefficient material, wherein the positivetemperature coefficient material comprises a first electrical resistancewhen the temperature of the positive temperature coefficient material isbelow a switching temperature and a second electrical resistance whenthe temperature of the positive temperature coefficient material isabove the switching temperature.

In at least one form, a surgical instrument can comprise a handle and anend effector, the end effector comprising a first jaw and a second jaw,wherein one of the first jaw and the second jaw is movable relative toother of the first jaw and the second jaw. The end effector can furthercomprise a first electrode positioned within the second jaw, a secondelectrode positioned within the second jaw, and a third electrodecomprised of a positive temperature coefficient material positionedwithin the first jaw, wherein the positive temperature coefficientmaterial comprises a first electrical resistance when the temperature ofsaid third electrode is below a switching temperature and a secondelectrical resistance higher than the first resistance when thetemperature of the third electrode is above the switching temperature.The surgical instrument can further comprise a controller configured toselectively electrically couple the first electrode and the secondelectrode with a power source.

In at least one form, a method of operating an electrosurgicalinstrument can comprise the steps of moving a first jaw toward a secondjaw in order to capture tissue between the first jaw and the second jaw,wherein the second jaw comprises a first electrode and a secondelectrode, and wherein the first jaw comprises an opposing electrodepositioned opposite the first electrode and the second electrode. Themethod further comprises the steps of applying a voltage potential tothe first electrode such that current can flow between the firstelectrode and the opposing electrode and can contract the tissuepositioned between the first electrode and the opposing electrode, andapplying a voltage potential to the second electrode after the voltagepotential has been at least initially applied to the first electrode. Inaddition, the method can further comprise advancing a cutting memberrelative to the first electrode and the second electrode.

The foregoing discussion should not be taken as a disavowal of claimscope.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features of the embodiments described herein are set forth withparticularity in the appended claims. The various embodiments, however,both as to organization and methods of operation, together withadvantages thereof, may be understood in accordance with the followingdescription taken in conjunction with the accompanying drawings asfollows.

FIG. 1 is a perspective view of an electrosurgical instrument.

FIG. 2 is a side view of a handle of the surgical instrument of FIG. 1with a half of a handle body removed to illustrate some of thecomponents therein.

FIG. 3 is a perspective view of an electrosurgical instrument.

FIG. 4A illustrates an end effector of an electrosurgical instrument inan open configuration.

FIG. 4B illustrates the end effector of FIG. 4A in a closedconfiguration.

FIG. 4C is a sectional view of a translatable member shaped like anI-beam which is configured to close the end effector of the surgicalinstrument of FIG. 3.

FIG. 5 is a cross-sectional view of an end effector including a firstjaw comprising electrodes and a second jaw positioned opposite the firstjaw.

FIG. 6 is a cross-sectional view of a jaw of an end effector includingan electrode comprising a porous material and an evaporable materialstored within the porous material.

FIG. 7 is a cross-sectional view of a jaw of an end effector includingan electrode comprising two layers of porous material and an evaporablematerial stored within the layers of porous material.

FIG. 8 is an exemplary temperature-resistance curve of an electrodecomprising an evaporable material.

FIG. 9 is an exemplary temperature-resistance curve of a polymeric PTCcomposition.

FIG. 10 is a cross-sectional detail view of an electrode that can beutilized with the end effector of FIG. 5.

FIG. 11 is a schematic of an electrical circuit configured to controlthe voltage potential applied to the electrodes of an end effector.

FIG. 12 is a diagram of an electrode that can be used in conjunctionwith the electrical circuit of FIG. 11.

FIG. 13 is a diagram of a jaw of an end effector comprising a pluralityof electrodes controlled by a plurality of electrical circuits.

FIG. 14 is a perspective view of an electrosurgical device.

FIG. 15A illustrates an end effector of an electrosurgical instrument inan open configuration.

FIG. 15B illustrates the end effector of FIG. 15A in a closedconfiguration.

FIG. 15C is a sectional view of a translatable member shaped like anI-beam which is configured to close the end effector of the surgicalinstrument of FIG. 14.

FIGS. 16A-16B illustrate an end effector of another electrosurgicalinstrument in a fully open position.

FIG. 17 illustrates the end effector of FIGS. 16A-16B in anintermediate, or partially closed, position.

FIG. 18 is an exploded view of the end effector of FIGS. 16A-16B in afully closed position.

FIGS. 19A-19C are sectional views of the end effector of FIGS. 16A-16Bin different modes of operation.

FIG. 20 is a detail view of an exemplary polymeric PTC compositioncomprising a polymer component having conductively clad, low densitymicrospheres therein.

FIG. 21 is a partial bottom view of a jaw of an electrosurgicalinstrument comprising a first PTC composition having a first switchingtemperature and a second PTC composition having a second switchingtemperature.

FIG. 22 is a cross-sectional view of the jaw of FIG. 21 taken along line22-22 in FIG. 21.

FIG. 23 is an electrical schematic of an electrosurgical instrumentcomprising the jaw of FIGS. 21 and 22.

FIG. 24 depicts a first temperature-resistance curve of a first PTCmaterial and a second temperature-resistance curve of a second PTCmaterial used in the same electrosurgical instrument.

FIG. 25 is a cross-sectional view of a first jaw and a second jaw of anelectrosurgical instrument, wherein the first jaw comprises a first PTCcomposition having a first switching temperature, a second PTCcomposition having a second switching temperature, and a third PTCcomposition having a third switching temperature.

FIG. 26 is an electrical schematic of the electrosurgical instrument ofFIG. 25.

FIG. 27 is a cross-sectional view of a first jaw and a second jaw of anelectrosurgical instrument comprising first and second electrodespositioned opposite to an electrode comprising a PTC composition.

FIG. 28 is a perspective view of an end effector of a surgicalinstrument comprising PTC materials embedded in first and second jaws ofthe end effector.

FIG. 29 is a cross-sectional view of the end effector of FIG. 28.

FIG. 30 is a detail view of the cross-sectional view of FIG. 29.

FIG. 31 is a partial perspective view of the end effector of FIG. 28 inan open configuration.

FIG. 32 is a side view of the end effector of FIG. 28 in an openconfiguration.

FIG. 33 is another perspective view of the end effector of FIG. 28 in anopen configuration.

FIG. 34 is a cross-sectional view of an electrode in accordance with atleast one embodiment, wherein the electrode comprises a first layerincluding a positive temperature coefficient (PTC) material and a secondlayer including a pressure sensitive (PS) material. The view depicts thePTC material in a condition to conduct electrical current therethroughwhile the PS material is depicted in a condition which inhibits the flowof electrical current therethrough.

FIG. 35 is a cross-sectional view of the electrode of FIG. 34. The viewdepicts both the PTC material and the PS material in a condition toconduct electrical current therethrough.

FIG. 36 is a cross-sectional view of the electrode of FIG. 34. The viewdepicts the PS material in a condition to conduct electrical currenttherethrough while the PTC material is depicted in a condition whichinhibits the flow of electrical current therethrough.

FIG. 37 is a cross-sectional view of the electrode of FIG. 34. The viewdepicts both the PTC material and the PS material in a condition whichinhibits the flow of electrical current therethrough.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate various embodiments of the invention, in one form, and suchexemplifications are not to be construed as limiting the scope of theinvention in any manner.

DETAILED DESCRIPTION

Various embodiments are directed to apparatuses, systems, and methodsfor the treatment of tissue. Numerous specific details are set forth toprovide a thorough understanding of the overall structure, function,manufacture, and use of the embodiments as described in thespecification and illustrated in the accompanying drawings. It will beunderstood by those skilled in the art, however, that the embodimentsmay be practiced without such specific details. In other instances,well-known operations, components, and elements have not been describedin detail so as not to obscure the embodiments described in thespecification. Those of ordinary skill in the art will understand thatthe embodiments described and illustrated herein are non-limitingexamples, and thus it can be appreciated that the specific structuraland functional details disclosed herein may be representative andillustrative. Variations and changes thereto may be made withoutdeparting from the scope of the claims.

Reference throughout the specification to “various embodiments,” “someembodiments,” “one embodiment,” or “an embodiment”, or the like, meansthat a particular feature, structure, or characteristic described inconnection with the embodiment is included in at least one embodiment.Thus, appearances of the phrases “in various embodiments,” “in someembodiments,” “in one embodiment,” or “in an embodiment”, or the like,in places throughout the specification are not necessarily all referringto the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments. Thus, the particular features, structures, orcharacteristics illustrated or described in connection with oneembodiment may be combined, in whole or in part, with the featuresstructures, or characteristics of one or more other embodiments withoutlimitation.

The entire disclosures of the following non-provisional United Statespatents are hereby incorporated by reference herein:

U.S. Pat. No. 7,381,209, entitled ELECTROSURGICAL INSTRUMENT;

U.S. Pat. No. 7,354,440, entitled ELECTROSURGICAL INSTRUMENT AND METHODOF USE;

U.S. Pat. No. 7,311,709, entitled ELECTROSURGICAL INSTRUMENT AND METHODOF USE;

U.S. Pat. No. 7,309,849, entitled POLYMER COMPOSITIONS EXHIBITING A PTCPROPERTY AND METHODS OF FABRICATION;

U.S. Pat. No. 7,220,951, entitled SURGICAL SEALING SURFACES AND METHODSOF USE;

U.S. Pat. No. 7,189,233, entitled ELECTROSURGICAL INSTRUMENT;

U.S. Pat. No. 7,186,253, entitled ELECTROSURGICAL JAW STRUCTURE FORCONTROLLED ENERGY DELIVERY;

U.S. Pat. No. 7,169,146, entitled ELECTROSURGICAL PROBE AND METHOD OFUSE;

U.S. Pat. No. 7,125,409, entitled ELECTROSURGICAL WORKING END FORCONTROLLED ENERGY DELIVERY; and

U.S. Pat. No. 7,112,201, entitled ELECTROSURGICAL INSTRUMENT AND METHODOF USE.

The entire disclosures of the following co-pending non-provisionalUnited States patent applications filed on even date herewith are herebyincorporated by reference herein:

U.S. patent application Ser. No. ______, entitled ELECTROSURGICALINSTRUMENT EMPLOYING PRESSURE-VARIATION ELECTRODES, Attorney Docket No.END6652USNP1/090288;

U.S. patent application Ser. No. ______, entitled ELECTROSURGICALINSTRUMENT EMPLOYING MULTIPLE POSITIVE TEMPERATURE COEFFICIENTELECTRODES, Attorney Docket No. END6652USNP2/090289; and

U.S. patent application Ser. No. ______, entitled ELECTROSURGICALINSTRUMENT EMPLOYING A PLURALITY OF ELECTRODES, Attorney Docket No.END6652USNP3/090290.

Various embodiments of systems and methods of the invention relate tocreating thermal “welds” or “fusion” within native tissue volumes. Thealternative terms of tissue “welding” and tissue “fusion” may be usedinterchangeably herein to describe thermal treatments of a targetedtissue volume that result in a substantially uniform fused-togethertissue mass, for example, in welding blood vessels that exhibitsubstantial burst strength immediately post-treatment. The strength ofsuch welds is particularly useful for (i) permanently sealing bloodvessels in vessel transection procedures; (ii) welding organ margins inresection procedures; (iii) welding other anatomic ducts whereinpermanent closure is required; and also (iv) for performing vesselanastomosis, vessel closure or other procedures that join togetheranatomic structures or portions thereof. The welding or fusion of tissueas disclosed herein is to be distinguished from “coagulation”,“hemostasis” and other similar descriptive terms that generally relateto the collapse and occlusion of blood flow within small blood vesselsor vascularized tissue. For example, any surface application of thermalenergy can cause coagulation or hemostasis—but does not fall into thecategory of “welding” as the term is used herein. Such surfacecoagulation does not create a weld that provides any substantialstrength in the treated tissue.

At the molecular level, the phenomena of truly “welding” tissue asdisclosed herein may result from the thermally-induced denaturation ofcollagen and other protein molecules in a targeted tissue volume tocreate a transient liquid or gel-like proteinaceous amalgam. A selectedenergy density is provided in the targeted tissue to cause hydrothermalbreakdown of intra- and intermolecular hydrogen crosslinks in collagenand other proteins. The denatured amalgam is maintained at a selectedlevel of hydration—without desiccation—for a selected time intervalwhich can be very brief. The targeted tissue volume is maintained undera selected very high level of mechanical compression to insure that theunwound strands of the denatured proteins are in close proximity toallow their intertwining and entanglement. Upon thermal relaxation, theintermixed amalgam results in protein entanglement as re-crosslinking orrenaturation occurs to thereby cause a uniform fused-together mass.

Various embodiments disclosed herein provide electrosurgical jawstructures adapted for transecting captured tissue between the jaws andfor contemporaneously welding the captured tissue margins withcontrolled application of RF energy. The jaw structures can comprise ascoring element which can cut or score tissue independently of thetissue capturing and welding functions of the jaw structures. The jawstructures can comprise first and second opposing jaws that carrypositive temperature coefficient (PTC) bodies for modulating RF energydelivery to the engaged tissue.

A surgical instrument can be configured to supply energy, such aselectrical energy, ultrasonic energy, and/or heat energy, for example,to the tissue of a patient. For example, various embodiments disclosedherein can comprise electrosurgical jaw structures adapted fortransecting captured tissue positioned between the jaws and forcontemporaneously welding margins of the captured tissue with thecontrolled application of RF energy, for example. Referring now to FIG.1, an electrosurgical instrument 100 is shown. Electrosurgicalinstrument 100 can comprise a proximal handle 105, a distal working endor end effector 110, and an introducer or elongate shaft 108 disposedtherebetween. End effector 110 may comprise a set of openable andcloseable jaws, such as an upper first jaw 120A and a lower second jaw120B, for example, which can comprise straight and/or curvedconfigurations. First jaw 120A and second jaw 120B may each comprise anelongate slot or channel 142A and 142B (see FIG. 3), respectively,therein disposed within their respective middle portions along axis 125,for example. As described in greater detail below, first jaw 120A andsecond jaw 120B may be coupled to an electrical source or RF source 145and a controller 150 through electrical leads in cable 152. Controller150 may be used to activate electrical source 145. In variousembodiments, the electrical source 145 may comprise an RF source, anultrasonic source, a direct current source, and/or any other suitabletype of electrical energy source, for example.

Moving now to FIG. 2, a side view of the handle 105 is shown with afirst handle body 106A (see FIG. 1) removed to illustrate some of thecomponents within second handle body 106B. Handle 105 may comprise alever arm, or trigger, 128 which may be pulled along a path 129. Leverarm 128 may be coupled to a movable cutting member disposed withinelongate shaft 108 by a shuttle 146 operably engaged to an extension 127of lever arm 128. The shuttle 146 may further be connected to a biasingdevice, such as spring 141, for example, which may also be connected tothe second handle body 106B, wherein the spring 141 can be configured tobias the shuttle 146 and thus the cutting member in a proximaldirection. When the cutting member is in a proximal position, the jaws120A and 120B can be urged into an open configuration as seen in FIG. 1by a jaw spring disposed between a portion of the jaws 120A and 120B,for example. Also, referring to FIGS. 1 and 2, a locking member 131 (seeFIG. 2) may be moved by a locking switch 130 (see FIG. 1) between alocked position in which the shuttle 146 can be prevented from movingdistally and an unlocked position in which the shuttle 146 may beallowed to freely move in the distal direction toward the elongate shaft108. The handle 105 can be any type of pistol-grip or other type ofhandle known in the art that is configured to carry actuator levers,triggers and/or sliders for actuating the first jaw 120A. Elongate shaft108 may have a cylindrical and/or rectangular cross-section and cancomprise a thin-wall tubular sleeve that extends from handle 105.Elongate shaft 108 may include a bore extending therethrough forcarrying actuator mechanisms configured to actuate the jaws and/or forcarrying electrical leads configured to conduct electrical energy toelectrosurgical components of end effector 110.

End effector 110 may be adapted for capturing, welding and transectingtissue. In various embodiments, at least one of first jaw 120A andsecond jaw 120B may be closed to capture or engage tissue therebetween.First jaw 120A and second jaw 120B may also apply compression to thetissue. Elongate shaft 108, along with first jaw 120A and second jaw120B, can be rotated a full 360° degrees, as shown by arrow 117,relative to handle 105 through one or more rotary contacts, for example.First jaw 120A and second jaw 120B can remain openable and/or closeablewhile rotated. Referring now to FIG. 1, end effector 110 may be coupledto electrical source 145 and controller 150. Controller 150 can regulatethe electrical energy delivered by electrical source 145 which in turndelivers electrosurgical energy to electrodes within the jaws 120A,120B. The energy delivery may be initiated by an activation button 124operably engaged with lever arm 128 and in electrically communicationwith controller 150 via cable 152. As mentioned above, theelectrosurgical energy delivered by electrical source 145 may compriseradiofrequency (RF) energy. As described in greater detail below, theelectrodes of the jaw members may carry variable resistive positivetemperature coefficient (PTC) bodies that are coupled to electricalsource 145 and controller 150. Additional details regardingelectrosurgical end effectors, jaw closing mechanisms, andelectrosurgical energy-delivery surfaces are described in the followingU.S. patents and published patent applications, all of which areincorporated herein in their entirety by reference and made a part ofthis specification: U.S. Pat. Nos. 7,381,209; 7,311,709; 7,220,951;7,189,233; 7,186,253; 7,125,409; 7,112,201; 7,087,054; 7,083,619;7,070,597; 7,041,102; 7,011,657; 6,929,644; 6,926,716; 6,913,579;6,905,497; 6,802,843; 6,770,072; 6,656,177; 6,533,784; and 6,500,176;and U.S. Pat. App. Pub. Nos. 2010/0036370 and 2009/0076506.

FIG. 3 illustrates an electrosurgical instrument 200 comprising a handleend 205, a shaft, or introducer, 206, and an end effector, or workingend, 210. Shaft 206 can comprise any suitable cross-section, such as acylindrical and/or rectangular cross-section, for example, and cancomprise a tubular sleeve that extends from handle 205. End effector 210can extend from shaft 206 and may be adapted for welding and transectingtissue. In various embodiments, end effector 210 can comprise anopenable and closeable jaw assembly which can, in various embodiments,comprise straight, curved, and/or any other suitably configured jaws. Invarious embodiments, the end effector 210 can comprise a first jaw 222Aand a second jaw 222B, wherein at least one of the jaws 222A and 222Bcan move relative to the other. In at least one embodiment, the firstjaw 222A can be pivoted about an axis relative to the second jaw 222B inorder close onto, capture, and/or engage tissue positioned between thejaws and apply a compression force or pressure thereto. In variousembodiments, the handle 205 can comprise a lever arm, or trigger, 228adapted to actuate a translatable member 240. More particularly, in atleast one embodiment, the lever arm 228 can be actuated in order to movemember 240 distally toward the distal end 211 of end effector 210 and,when member 240 is advanced distally, member 240 can contact first jaw222A and move it downwardly toward second jaw 222B, as illustrated inFIG. 4B. In at least one embodiment, the translatable member 240 cancomprise a proximal rack portion and the lever arm 228 can comprise aplurality of gear teeth which can be configured to drive the proximalrack portion of translatable member 240 distally. In certainembodiments, rotation of the lever arm 228 in the opposite direction candrive the translatable member 240 proximally.

As described above, the translatable member 240 can be configured tocontact first jaw 222A and pivot jaw 222A toward second jaw 222B. Invarious embodiments, referring now to FIGS. 4A-4C, the distal end ofreciprocating member 240 can comprise a flanged “I”-beam configured toslide within a channel 242 in the jaws 222A and 222B. Referringprimarily to FIG. 4C, the I-beam portion of member 240 can comprise anupper flange 250A, a lower flange 250B, and a center, or intermediate,portion 251 connecting the flanges 250A and 250B. In at least oneembodiment, the flanges 250A and 250B and the center portion 251 candefine “c”-shaped channels on the opposite sides of member 240. In anyevent, in various embodiments, the flanges 250A and 250B can defineinner cam surfaces 252A and 252B, respectively, for slidably engagingoutward-facing surfaces 262A and 262B of jaws 222A and 222B,respectively. More particularly, the inner cam surface 252A can comprisea suitable profile configured to slidably engage the outer surface 262Aof first jaw 222A and, similarly, the inner cam surface 252B cancomprise a suitable profile configured to slidably engage the outersurface 262B of second jaw 222B such that, as translatable member 240 isadvanced distally, the cam surfaces 252A and 252B can co-operate to camfirst jaw member 222A toward second jaw member 222B and configure theend effector 240 in a closed configuration. As seen in FIG. 4B, jaws222A and 222B can define a gap, or dimension, D between the first andsecond electrodes 265A and 265B of jaws 222A and 222B, respectively,when they are positioned in a closed configuration. In variousembodiments, dimension D can equal a distance between approximately0.0005″ to approximately 0.005″, for example, and, in at least oneembodiment, between approximately 0.001″ and approximately 0.002″, forexample.

As discussed above, the translatable member 240 can be at leastpartially advanced in order to move the first jaw 222A toward the secondjaw 222B. Thereafter, the movable member 240 can be advanced furtherdistally in order to transect the tissue positioned between the firstjaw 222A and the second jaw 222B. In certain embodiments, the distal, orleading, end of the I-beam portion of 240 can comprise a sharp, orknife, edge which can be configured to incise the tissue. Before,during, and/or after the member 240 is advanced through the tissue,electrical current can be supplied to the electrodes in the first andsecond jaw members in order to weld the tissue, as described in greaterdetail further below. In various circumstances, the operation of thetrigger 228 can advance the knife edge of the cutting member 240 to thevery distal end of slot or channel 242. After the cutting member 240 hasbeen sufficiently advanced, the trigger 288 can be released and movedinto its original, or unactuated, position in order to retract thecutting member 240 and allow first jaw 222A to move into is openposition again. In at least one such embodiment, the surgical instrumentcan comprise a jaw spring configured to bias the first jaw 222A into itsopen position and, in addition, a trigger spring configured to bias thetrigger 228 into its unactuated position.

In various embodiments, further to the above, the surgical instrumentcan comprise a first conductor, such as an insulated wire, for example,which can be operably coupled with the first electrode 265A in first jawmember 222A and, in addition, a second conductor, such as an insulatedwire, for example, which can be operably coupled with the secondelectrode 265B in second jaw member 222B. In at least one embodiment,referring again to FIG. 3, the first and second conductors can extendthrough shaft 206 between an electrical connector in handle 205 and theelectrodes 265A and 265B in the end effector 210. In use, the first andsecond conductors can be operably coupled to electrical source 245 andcontroller 250 by electrical leads in cable 252 in order for theelectrodes 265A and 265B to function as paired bi-polar electrodes witha positive polarity (+) and a negative polarity (−). More particularly,in at least one embodiment, one of the first and second electrodes 265Aand 265B can be operably coupled with a positive (+) voltage terminal ofelectrical source 245 and the other of the first and second electrodes265A and 265B can be electrically coupled with the negative voltage (−)terminal of electrical source 245. Owing to the opposite polarities ofelectrodes 265A and 265B, current can flow through the tissue positionedbetween the electrodes 265A and 265B and heat the tissue to a desiredtemperature. In certain embodiments, the cutting member 240 can act asan electrode when it is electrically coupled to a positive terminal ornegative terminal of the source 245, and/or any suitable ground.

In various embodiments, referring now to FIG. 5, an end effector of asurgical instrument, such as end effector 310, for example, can comprisea first jaw 322A and a second jaw 322B, wherein at least one of the jaws322A, 322B can be moved relative to the other in order to capture tissuetherebetween. Each of the jaws 322A and 322B can comprise one or moreelectrodes which can be configured to permit current to flow between theelectrodes and/or between an electrode and another portion of the endeffector 310 when a voltage potential is applied to at least one of theelectrodes. In at least one embodiment, current can flow betweenelectrodes 381 and electrodes 380, for example. In certain embodiments,current can flow between the electrodes 381 and at least one of theframe member 328A of first jaw 322A, the frame member 328B of second jaw322B, and/or the cutting member 340, for example. In at least one suchembodiment, the electrodes 381 can be electrically coupled with thepositive terminal of a power source while the electrodes 380, the framemembers 328A, 328B, and/or the cutting member 140 can be electricallycoupled with the negative terminal of the power source and/or anysuitable ground. In certain embodiments, the surgical instrument caninclude a first conductor electrically coupled with the power source andthe electrodes 380 and, in addition, a second conductor electricallycoupled with the power source and the electrodes 381 such that a voltagepotential can be applied to one or more of the electrodes 380 and 381and a circuit can be completed therebetween. In any event, as describedabove, current flowing through the electrodes 381 and the tissuepositioned intermediate the jaws 322A and 322B can generate heat andraise the temperature of the tissue and electrodes 381.

In various embodiments, one or more electrodes of the end effector 310,such as electrodes 381, for example, can comprise an evaporable materialwhich can evaporate when the temperature of the electrodes 381 reach theboiling point of the evaporable material. In at least one suchembodiment, referring to FIG. 6, an electrode 381 can comprise a porousmaterial, or matrix, 390 and an evaporable material stored within theporous material 390. The porous material 390 can comprise an insulative,or relatively non-conductive material, such as, for example, elastomericand thermoplastic polysaccharides, examples of which include celluloseacetate and cellulose nitrate, for example, fibrous hydrophilictextiles, open celled foams, examples of which include high internalphase emulsion (HIPE) foams including those disclosed in U.S. Pat. Nos.5,563,179 and 5,387,207, the entire disclosures of which areincorporated by reference herein, thin-until-wet materials includingthose described in U.S. Pat. No. 5,108,383, the entire disclosure ofwhich is incorporated by reference herein, porous glass frit materials,examples of which include silicon dioxide based glass mixes, and/orporous ceramic frit materials, such as ceramics comprising titaniumdioxide, for example. The material, or materials, comprising porousmaterial 390 can have a sufficient porosity in order to allow aconductive evaporable material to be absorbed into, or reside within,the pores of the porous material 390. In at least one embodiment, theconductive evaporable material can comprise saline, such as isotonicsaline, for example. In various embodiments, the evaporable conductivematerial can comprise an electrical conductivity and/or a thermalconductivity which is the same order of magnitude, and/or within anorder of magnitude, as the conductivities of the tissue, the porousmaterial, and/or the opposing electrodes within the end effector, forexample. In use, the conductive evaporable material can conduct currentthrough the electrode 381 eventhough the porous material 390 may benon-conductive. Referring again to FIG. 6, an electrode 381 can comprisea conductive member 391 positioned on a first, or bottom, side of theporous material 390 and a conductive surface 392 positioned on a second,or top, side of the porous material 390. Further to the above, invarious embodiments, a conductor can be electrically coupled to, one, apositive voltage terminal of a power source as described above, and,two, the conductive member 391 such that the conductor can apply avoltage potential to a first side of the electrode 381. In variouscircumstances, as a result, current can flow from the first conductivemember 391, through the conductive evaporable material within the porousmaterial 390, and through the conductive surface 392. When tissue ispositioned against the conductive surface 392, the current can flowthrough the tissue into an opposing electrode 380, for example. Variousalternative embodiments are envisioned in which the conductive member391 is electrically coupled with a negative terminal of a power sourceand/or any suitable ground.

In various embodiments, further to the above, the conductive member 391can be configured to attach the electrode 381 to the frame member 328Bof second jaw 322B. In at least one embodiment, the conductive member391 can comprise copper and/or brass which can be used to braze theelectrode 381 to second jaw member 322B, while, in certain embodiments,the conductive member 391 can comprise a conductive adhesive, such asfilled urethane acrylates, filled epoxies, and/or filled silicones, forexample, which can adhere the electrode 381 to the jaw member 322B. Inat least one embodiment, transfer tape, including 3M transfer tape whichcan be purchased from the Minnesota Mining and Manufacturing Company,can be utilized to adhere the electrode 381 to the jaw member 322B, forexample. In some embodiments, fasteners, such as screws, for example,can be utilized to secure the electrode 381 to the frame member 328B. Incertain embodiments, the electrode 381 can include sidewalls 393 whichcan be comprised of an electrically insulative material, such as silicondioxide, for example. In at least one such embodiment, the sidewalls 393can form a housing which can at least partially enclose the porousmaterial 390. In various embodiments, the housing can comprise a firstopening such that the conductive member 391 can be in contact with thefirst side of the porous material 390 and, in addition, a second openingsuch that tissue can contact conductive surface 392. In certainembodiments, the conductive surface 392 can comprise a tissue-contactingpad which can comprise a tissue-contacting surface configured to contactthe tissue positioned intermediate the first jaw 322A and the second jaw322B. In at least one such embodiment, the tissue-contacting pad cancomprise a polymeric material having conductive particles dispersedtherein, for example, wherein, in certain embodiments, the secondconductive surface 392 can comprise a positive temperature coefficient(PTC) material as described below. In various embodiments, the frameportion of the jaw 322B surrounding the electrode 381 can be comprisedof silicon, for example.

When a voltage potential is applied to electrode 381 and current flowstherethrough, as described above, heat can be generated within theelectrode 381 and the tissue positioned intermediate the jaws 322A and322B. As the temperature of the electrode 381 increases, referring nowto FIG. 8, the electrical resistance or impedance of the electrode 381can also increase. Such an increase in temperature and resistance isrepresented by the portion of temperature-resistance curve in FIG. 8between points X and Y. As the reader will note, the change inresistance of electrode 381 can be linearly proportional, or at leastsubstantially linearly proportional, to the change in temperature ofelectrode 381, although other embodiments are envisioned in which thisrelationship is geometrically proportional. In at least one embodiment,the change in resistance can be incremental with respect to the changein temperature between points X and Y. In any event, once thetemperature of the electrode 381 reaches the boiling point temperatureTb of the conductive evaporable material contained within the porousmaterial 390, the evaporable material can evaporate. As the conductiveevaporable material evaporates, the resistance of the electrode 381 canincrease. More particularly, as the conductive material evaporates,fewer conductive, or electrically percolative, paths of the conductiveevaporable material may exist in the porous material 390 therebyincreasing the resistance of the electrode. In at least one embodiment,as discussed above, the porous material 390 can be comprised of anon-conductive, or at least substantially non-conductive, material suchthat, once the conductive material has evaporated, the electricalresistance of the electrode 381, which is substantially the electricalresistance of the porous material 390 at this point, may be sufficientlyhigh so as to prevent, or at least substantially inhibit, current fromflowing through the electrode 381.

The transition of electrode 381 between being conductive andnon-conductive, or at least substantially non-conductive, as describedabove, can be represented by the portion of the temperature-resistancecurve between points Y and Z in FIG. 8. As the reader will note, theportion of the curve between points Y and Z depicted in FIG. 8 can beasymptotical, or at least substantially asymptotical, such that theslope of the temperature-resistance curve between points Y and Z issignificantly higher than the slope of the curve between points X and Y.In various circumstances, the evaporation of the conductive material maytake a period of time to occur and, during such time, the temperature ofthe electrode 381 may remain constant, or at least substantiallyconstant, at the boiling point temperature Tb. In at least oneembodiment, the conductive evaporable material can comprise a boilingpoint temperature of approximately 100 degrees Celsius, for example, at1 atm atmospheric pressure. In various embodiments, the conductiveevaporable material can comprise a boiling point temperature ofapproximately 105 degrees Celsius, approximately 110 degrees Celsius,approximately 115 degrees Celsius, or approximately 120 degrees Celsius,for example. In various circumstances, the boiling point of theconductive evaporable material can depend on the surrounding atmosphericpressure. In any event, in certain circumstances, the evaporation of theconductive material can begin to occur at certain locations, or hotspots, in the electrode 381 before the conductive material begins toevaporate at other locations within the electrode 381. In some suchcircumstances, the flow of current through electrode 381, and the tissuepositioned thereagainst, can be reduced at the locations which havealready reached the boiling point temperature of the conductiveevaporable material, whereas the current can continue to flow throughthe portions of the electrode 381 which have not reached the boilingpoint temperature of the conductive evaporable material. In variousembodiments, as a result, each electrode can comprise a means for animmediate and localized response to the heat being generated within theelectrode and/or tissue positioned against the tissue. In certaincircumstances, the top of porous material 390, or the portion of porousmaterial 390 closest to surface 392, can reach the boiling pointtemperature of the conductive evaporable material before the bottom ofthe porous material 390, for example, reaches the boiling pointtemperature. In such circumstances, the evaporable material mayevaporate, or at least substantially evaporate, from the top portion ofthe porous material 390 creating a short, or break, in the conductivepaths between the conductive material 391 and the conductive surface 392before the remainder of the electrode 381 reaches the boiling pointtemperature. In any event, once the conductive evaporable material hasevaporated, or at least substantially evaporated, from the porousmaterial 390, and/or once the resistance of the electrode 381 hasincreased between a first resistance (Point Y) and a substantiallyhigher resistance (Point Z), the resistance of the electrode 381 canincrease incrementally as the temperature of the electrode 381increases.

In various embodiments, further to the above, the boiling pointtemperature Tb of the conductive evaporable material can comprise aswitching temperature of the electrode 381 in which, as discussed above,the resistance of the electrode 381 can increase significantly. Incertain embodiments, the electrical resistance of the electrode canincrease between a first resistance (Point Y), for example, to a secondresistance (Point Z), for example. In at least one embodiment, the firstresistance (Point Y) can be approximately 5 ohms, approximately 10 ohms,approximately 15 ohms, approximately 20 ohms, approximately 25 ohms,approximately 30 ohms and/or within a range between approximately 5 ohmsand approximately 30 ohms, for example. In at least one embodiment, thesecond resistance (Point Z) can be approximately 140 ohms, approximately145 ohms, approximately 150 ohms, approximately 155 ohms, approximately160 ohms and/or within a range between approximately 140 ohms andapproximately 160 ohms, for example. In certain embodiments, the secondresistance (Point Z) can be approximately 450 ohms, for example. Invarious circumstances, the second, or switched, resistance can besignificantly higher than the first resistance such that current flowingthrough the electrode 381, if any current flows at all, may not be ableto irreversibly alter and/or therapeutically treat the tissue positionedbetween the first and second jaws 322A, 322B. In certain embodiments,the switched, second electrical resistance can be approximately 2, 5,10, 100, or 1000 times larger than the first, unswitched, resistance. Invarious circumstances, as described above, the conductive evaporablematerial can transition between a liquid and a vapor wherein the vaporcan outgas from the porous material into the environment surrounding theend effector 310. In certain embodiments, the heat created within theelectrode 381 can cause the conductive evaporative material to migrateout of the porous material 390 thereby increasing the electricalresistance of the electrode 381. In at least one such embodiment, atemperature differential created within the electrode 381 can cause theconductive evaporable material to migrate away, or possibly toward, thehigher temperature within the electrode 381. In certain circumstances,the conductive evaporable material can flow, withdraw, and/or recedefrom the porous material 390 at certain temperatures of the electrode381.

In various circumstances, the electrodes 381 can cool below, be cooledbelow, and/or be permitted to cool below the boiling point temperatureof the conductive evaporable material. In at least some circumstances,the evaporated conductive material can recondense and can be reabsorbedby the porous material 390. In certain circumstances, however, at leasta large portion of the evaporated material may be unrecoverable. In atleast one such circumstance, the porous material 390 can be configuredto absorb blood and/or other surrounding conductive fluids, for example,from the surgical site once the temperature of the electrodes 381 dropsbelow the boiling point temperature of such fluids. In at least oneembodiment, a supply of electrolytic fluid can be supplied to thesurgical site and/or end effector 310 such that the electrodes 381 havea ready supply of conductive fluids to replenish the evaporated fluids.Such a surgical instrument can comprise a pump and/or a reservoir whichcan be configured to supply an evaporable liquid to the electrodes 381via one or more supply conduits extending through and/or along the shaftof the surgical instrument. In any event, the newly absorbed conductivematerial can allow current to be conducted through the electrodes 381and, as a result, allow the electrodes 381 to be used to treat tissueonce again. In certain embodiments, each electrode 381 can comprise asealed, or an at least substantially sealed, housing wherein the porousmaterial 390 and the conductive evaporable material can be containedtherein. In at least one such embodiment, the conductive evaporablematerial can be in a liquid state within the porous material 390 whenthe temperature of the electrode is below the boiling point temperatureof the conductive evaporable material and, in the event that theconductive evaporable material were to leak or flow out of the porousmaterial 390, the conductive evaporable material could be containedwithin the sealed housing. As the temperature of the electrode isincreased during use, the conductive evaporable material can evaporateinto a vapor; however, the evaporated material can be contained, or atleast substantially contained, within the sealed housing such that, whenthe temperature of the electrode cools below the boiling pointtemperature of the conductive evaporable material, the conductiveevaporated material can recondense and can be reabsorbed by the porousmaterial. In at least one embodiment, the entirety of the conductiveevaporable material can be recovered and reabsorbed by the porousmaterial, although other embodiments are envisioned in which asubstantial portion, or only a portion, of the conductive evaporablematerial can be recovered and reabsorbed.

In various embodiments, a surgical instrument can comprise an endeffector which can be detached from the surgical instrument and replacedwith another end effector, wherein such end effectors can compriseelectrodes having at least one porous material and conductive evaporablematerial such as those disclosed throughout this application. In atleast one embodiment, an initial end effector can be attached to theshaft of the surgical instrument and, after the end effector has beenused and at least a portion of the evaporable material has beenevaporated therefrom, the surgical instrument can be removed from thepatient and the initial end effector can be detached from the surgicalinstrument. Thereafter, another end effector can be attached to thesurgical instrument, wherein the surgical instrument can then bereinserted into the surgical site and used once again. In at least onesuch embodiment, the electrodes of the end effector can have a fullsupply of evaporable material which can allow the surgical instrument tobe used once again as described herein.

In various embodiments, an electrode can comprise more than one porousmaterial and/or more than one conductive evaporable material. In atleast one such embodiment, a first conductive evaporable material and asecond conductive evaporable material can be stored within a porousmaterial, wherein the first and second evaporable materials can havedifferent boiling point temperatures, for example. During use, in atleast one such embodiment, the temperature of the electrode can increaseuntil it reaches the first boiling point temperature wherein, at such atemperature, the first conductive evaporable material can evaporate. Invarious embodiments, the second boiling point temperature of the secondconductive evaporable material can be higher than the first boilingpoint temperature such that the second conductive evaporable materialcan remain unevaporated within the porous material eventhough thetemperature of the electrode may have reached and/or exceeded the firstboiling point temperature. In various circumstances, the evaporation ofthe first conductive evaporable material can cause the electricalresistance of the electrode to increase between a first resistance and asecond resistance. Owing to the presence of the second conductiveevaporable material within the porous material, however, the secondelectrical resistance of the electrode can be such that sufficientcurrent can be conducted through the electrode in order to sufficientlytreat the tissue. Once the temperature of the electrode reaches thesecond boiling point temperature, however, the second conductivematerial can evaporate and the electrical resistance of the electrodecan increase to a third electrical resistance which makes the electrodenon-conductive, or at least substantially non-conductive. In variousembodiments, further to the above, the first and second conductiveevaporable materials can have different electrical conductivities. In atleast one embodiment, for example, the first conductive evaporablematerial can comprise a first electrical conductivity which is higherthan the second conductive evaporable material. In at least one suchembodiment, the evaporation of the first conductive material before theevaporation of the second conductive material can leave the electrodewith a conductive material having a lesser electrical conductivitythereby resulting in a higher resistance of the electrode. In certainembodiments, the conductive material having a higher boiling pointtemperature can have a higher electrical conductivity than theelectrical conductivity of the material having a lower boiling pointtemperature.

In various embodiments, the porous material, or matrix, of theelectrodes disclosed in the present application may be sufficientlymechanically robust in order to withstand the clamping pressure of thejaws. In addition, such electrodes may be mechanically and/or chemicallystable to withstand at least 140 degrees Celsius in a steam atmosphere.Furthermore, the porous material may be able to rapidly absorb liquidmoisture and/or rapidly desorb vapor. In various embodiments, rapidabsorption and desorption of the conductive evaporable material can beenhanced via chemistry. For example, the surface tension on the surfacesof the pores can be modified via functionalization of polymer chainscomprising the porous material. In at least one such circumstance, thesurface of the polymer can be treated with a plasma processing techniquein order to create functional groups within the surface of the polymermaterial. In certain embodiments, the surface of the porous material canbe treated via radiation functionalization. In various embodiments, thesurface of the porous material can be coated with surfactants, forexample.

In various embodiments, the porous material, or matrix, of theelectrodes disclosed in the present application may comprise one or moresalts therein. In at least one such embodiment, the salts can be mixedinto the porous material, such as a polymer material, for example,before the mixture is formed into an electrode, such as by an injectionmolding process, for example. In any event, such salts can pull fluidsinto the matrix via osmotic gradients, for example. In certainembodiments, referring now to FIG. 7, an electrode, such as electrode481, for example, can comprise a first porous material, or base layer,490 and a second porous material, or top layer, 494, wherein the toplayer 494 can be positioned against the tissue to be treated. In atleast one embodiment, the base layer 490 can comprise a high saltcontent which can pull fluid into the base layer 490 through the toplayer 494. The base layer 490 can hydrate the top layer 494 and act as areservoir to supply the top layer 494 as and/or after the evaporablematerial is depleted from the top layer 494. In various embodiments, thetop layer 494 can be thinner than the base layer 490 wherein, in atleast one embodiment, the thicker base layer 490 can be sufficientlyrigid to support the thinner top layer 494. In use, the thinner toplayer 494 can be designed to be rapidly depleted of its water content,for example, and decrease its effective electrical conductivity as thetemperature of the top layer 494 exceeds the phase transitiontemperature of the water, which can be approximately 100 degrees Celsiusin a multitude of circumstances, for example. In various embodiments,the top layer 494 can be comprised of polyamide foam, such as Monodur,for example, and/or porous polytetrafluoroethylene (PTFE), for example.The base layer 490 can be comprised of glass frit and/or wovencellulose, for example, and the osmotic generating salts can becomprised of potassium chloride (KCl), sodium sulphate (Na2SO4),ammonium dihydrogen phosphate (NH4)H2PO4, and/or a calcium chloride suchas CaCl2-2H2O, for example.

Referring again to FIG. 5, electrodes 381 can be mounted to second jaw322B which is positioned opposite the first jaw 322A. In variousembodiments, the first jaw 322 a can be comprised of silicon, theentirety of which, or at least substantial entirety of which, cancomprise a return, or negative, electrode. In various embodiments,referring now to FIG. 10, a surgical instrument can comprise anelectrode, such as electrode 581, for example, which can comprise a topsurface, or pad, which can be positioned opposite the first jaw 322A. Inat least one embodiment, the electrode 581 can comprise atissue-contacting pad 592 which can be electrically coupled to thepositive terminal of a power source via electrical conductors, or leads,595, for example. In use, as described above, the tissue-contacting pad592 can be polarized by the power source in order to treat the tissuepositioned thereagainst. In various embodiments, the pad 592 can bemounted to electrode 581 on electrically insulative members 593 whichcan be comprised of silicon dioxide, for example. The insulative members593 can comprise part of an electrode frame also comprising insulativemembers 595, for example. In certain embodiments, the electrode 581 canfurther comprise a connective layer 591 which can be used to mount theelectrode 581 to second jaw 322B, for example. In at least one suchembodiment, the connective layer 591 can comprise braze and/or adhesive,for example. In certain embodiments, ceramic inserts can be positionedbetween the electrodes 581 and the frame of the second jaw member, forexample.

In various embodiments, referring now to FIGS. 11 and 12, a surgicalinstrument can comprise an integrated JFET to control the currentflowing through the electrode 581, and/or any other suitable electrode.An exemplary schematic of an electrical circuit 650 is provided in FIG.11 which can be utilized in connection with an electrosurgicalinstrument, including the electrosurgical instruments disclosed herein,wherein the electrical circuit 650 can be configured to sense thetemperature of the end effector jaws, the electrodes 680, 681, and/orthe tissue positioned intermediate the electrodes 680, 681, and modulatethe voltage applied to, and the current flowing through, the electrodes680, 681 in view of the sensed temperature. Owing to the modulatedcurrent flowing through the electrodes 680, 681, the heat generated bythe current can be modulated. More particularly, as described in greaterdetail below, the electrical circuit 650 can be configured to decreasethe magnitude of current flowing between the electrodes 680, 681 and, asa result, reduce the heat generated by such current. Correspondingly, asalso described in greater detail below, the electrical circuit 650 canbe configured to increase the magnitude of the current flowing betweenthe electrodes 680, 681 and, as a result, permit the heat generated bysuch current to increase.

Further to the above, the electrical circuit 650 can comprise a powersupply and/or the secondary wiring of a transformer 652 powered by agenerator, for example, which can be configured to apply a voltagepotential to diode bridge 654. More particularly, in at least oneembodiment, the surgical instrument can further comprise a trigger,and/or trigger switch 628, which can be configured to close one or morecontacts and electrically couple the transformer 652 to the diode bridge654. Diode bridge 654, as is well known in the art, can be configured torectify the input voltage supplied to the electrical circuit 650 by thegenerator. In at least one such embodiment, the diode bridge 654 can beconfigured to rectify an alternating sinusoidal voltage wherein,although not illustrated, the circuit 650 can further comprise one ormore capacitive elements which can smooth ripples within the rectifiedvoltage, for example. In any event, the diode bridge 654 can comprise arectified positive voltage terminal 653 and a rectified negative voltageterminal 655. Electrically coupled in parallel to the positive terminal653 and the negative terminal 655 is a temperature sensing circuit 656which can detect the temperature of the electrode 681 and/or the jawsupporting electrode 681, for example. Various temperature sensingcircuits that can provide temperature sensing circuit 656 are disclosedin U.S. Pat. No. 3,703,651, entitled TEMPERATURE-CONTROLLED INTEGRATEDCIRCUITS, which issued on Nov. 21, 1972, and U.S. Pat. No. 6,789,939,entitled TEMPERATURE SENSOR AND METHOD FOR OPERATING A TEMPERATURESENSOR, which issued on Sep. 14, 2004, the entire disclosures of whichare incorporated by reference herein. Various other temperature sensingcircuits are commercially available from National SemiconductorCorporation, Santa Clara, Calif.

In various embodiments, further to the above, the electrical circuit 650can further comprise a junction gate field-effect transistor (JFET) 660which can be controlled by the temperature sensing circuit 656. Moreparticularly, the JFET 660 can comprise a source terminal 661electrically coupled to the positive terminal 653 of the diode bridge654, a drain terminal 662 electrically coupled to the electrode 681,and, in addition, a gate terminal 663 which can be in electricalcommunication with the temperature sensing circuit 656, wherein theelectrical resistance, or impedance, between the source terminal 661 andthe drain terminal 662 can be controlled by the voltage potentialapplied to the gate terminal 663 by the temperature sensing circuit 656.In at least one such embodiment, the JFET 660 can include a channelcomprised of an n-type semiconductor material, for example, whereincurrent can flow through the channel between the source terminal 661 andthe drain terminal 662, and wherein the gate terminal 663 can bepositioned relative to the channel such that an electric field producedby the gate terminal 663 can affect the flow of current through thechannel. More particularly, when the gate terminal 663 is polarized, orthe polarization of the gate terminal 663 is changed, the gate terminal663 can produce an electric field which can, at least temporarily,affect the semiconductor material such that the resistance between thesource terminal 661 and the drain terminal 662 is affected. In certainembodiments, an increase in the voltage potential applied to gateterminal 663 can increase the electrical resistance while, in otherembodiments, an increase in the voltage potential applied to gateterminal 663 can decrease the electrical resistance, for example. In anyevent, when the resistance between the source terminal 661 and the drainterminal 662 is increased, the current flowing between the sourceterminal 661 and the drain terminal 662 can be decreased.

In operation, in at least one embodiment, the temperature sensingcircuit 665 can be configured to apply a voltage potential to the gateterminal 663 of JFET 660 which is a function of the temperature sensedby the temperature sensing circuit 665. The temperature sensing circuit665 can be configured to apply a first voltage potential to the gateterminal 663 when it detects a first temperature, a second voltagepotential when it detects a second temperature, and a third voltagepotential when it detects a third temperature, and so forth. In variousembodiments, the temperature sensing circuit 665 can decrease thevoltage potential applied to the gate terminal 663 as the temperature ofthe electrode 681 increases. For example, the temperature sensingcircuit 665 can be configured to apply a first voltage potential to thegate terminal 663 when a first temperature is detected by thetemperature sensing circuit and, in addition, a second voltagepotential, which is lower than the first voltage potential, when thetemperature sensing circuit 665 detects a second temperature which ishigher than the first temperature. Correspondingly, the temperaturesensing circuit 665 can increase the voltage potential applied to thegate terminal 663 as the temperature of the electrode 681 decreases. Insuch embodiments, the resistance, or impedance, of the JFET 660 channelcan increase when the temperature of the electrode 681 increases,thereby ‘constricting’ the current that can flow therethrough, anddecrease when the temperature of the electrode 681 decreases, thereby“relaxing' the constriction of the current flowing through the channel.In various alternative embodiments, the JFET can be configured such thatan increase in voltage potential applied to the gate of the JFETincreases the resistance of the JFET channel while a decrease in voltagepotential applied to the gate of the JFET decreases the resistance ofthe JFET channel. In certain embodiments, the channel of JFET 660 cancomprise a p-type semiconductor material.

In various circumstances, further to the above, the magnitude of thecurrent flowing through the channel of JFET 660 (drain-source current)can be a function of, one, the voltage differential between the sourceterminal 661 and the drain terminal 662 (drain-source voltage) and, two,the voltage of the gate terminal 663 as discussed above. In variousembodiments, the drain-source current can be directly proportional tothe drain-source voltage and/or the gate voltage. In certaincircumstances, the relationship between the drain-source current and thedrain-source voltage can comprise at least two operating regions forcertain values of the drain-source voltage and the gate voltage, forexample. More particularly, the operating curve of a JFET device cancomprise what are known as a linear region and a saturation region,wherein the relationship between the drain-source current and thedrain-source voltage is different in each of these regions. In variousembodiments, the relationship between the drain-source current and thegate voltage in the saturation region of the JFET operating curve can belinearly, or at least substantially linearly, proportional, for example.

In various embodiments, referring now to FIG. 12, an end effector of asurgical instrument can comprise a jaw 622 b which can include theelectrode 681 and the JFET 660, for example. In at least one suchembodiment, the source terminal 661 can comprise an elongate conductorextending longitudinally from the proximal end 621 of the jaw 622B tothe distal end 623 of jaw 622B. As outlined above, the source terminal661 can be electrically coupled to the rectified positive voltageterminal 653 of diode bridge 654 via a conductor, or lead, extendingtherebetween, for example. Similarly, the gate terminal 663 can comprisean elongate member which also extends from the proximal end 621 to thedistal end 623 of jaw 622B, for example, wherein the gate terminal 663can be electrically coupled to an output of the temperature sensingcircuit 656 via a conductor, or lead, extending between the gateterminal 663 and the temperature sensing circuit 656, for example. Invarious embodiments, further to the above, the JFET 660 can include achannel, such as channel 665, for example, which can be comprised of atleast one semiconductor material, for example. In at least one suchembodiment, the source terminal 661 and the drain terminal 662 of theJFET 660 can be positioned on opposite sides of the gate terminal 663,wherein the electrode 681 can be positioned against, and/or otherwise inelectrical communication with, the drain terminal 662. Similar to theabove, the electrode 681 can extend longitudinally along the drainterminal 662 from the proximal end 621 to the distal end 623 of the jaw622B, for example. As discussed above, the gate terminal 663 can bepolarized to create, or change, an electric field, within the channel665 in order to alter the flow of current through the channel 665between the source terminal 661 and the drain terminal 662. In variousembodiments, further to the above, the jaw 622A can comprise one or moreinsulative members 625, for example, which can be configured toelectrically insulate the source terminal 661 from the drain terminal662 such that the current flows through the channel 665. Although notillustrated, in various embodiments, the diode bridge 654 can bepositioned in the handle, the shaft, and/or the end effector of thesurgical instrument, although larger diodes may be suitably accommodatedin the handle of the surgical instrument, for example.

In various embodiments, the jaw 622B can comprise a first electrode 681positioned along a first side of a channel configured to receive acutting member and, in addition, a second electrode 681 positioned alonga second side of the cutting member channel. In at least one embodiment,each of the electrodes 681 can be operably coupled with a circuit 650which can be configured to independently monitor the temperature of theelectrodes 681 and independently adjust the current flowing through theelectrodes 681. In at least one such embodiment, the current flowingthrough, and the heat generated by, the entire length of each electrode681 can be adjusted simultaneously. In various embodiments, referringnow to FIG. 13, a jaw 722B, for example, can comprise a plurality ofelectrodes 681 positioned on a first side of a cutting member channel742 and a plurality of electrodes 681 positioned on a second side of acutting member channel 742. In at least one such embodiment, each of theelectrodes 681 can be operably coupled with a control circuit 650,wherein each control circuit 650 can be configured to independentlymonitor and control the temperature of their respective electrodes 681.In various circumstances, as a result, the current flowing through, andthe heat generated by, each electrode 681 can be adjusted independentlyof one another.

As described above, various embodiments can utilize integrated JFETdevices for controlling the current flowing through the electrodes of anelectrosurgical device. In certain embodiments, any other suitable fieldeffect transistors and/or bipolar transistors could be utilized. In atleast one such embodiment, a control circuit can comprise a temperaturesensing circuit, such as temperature sensing circuit 656, for example,and a bipolar junction transistor, wherein the bi-polar junctiontransistor can comprise an emitter terminal, a collector terminal, and abase terminal, and wherein the temperature sensing circuit is operablycoupled with the base terminal such that the temperature sensor canapply a voltage potential to the base terminal and affect the flow ofcurrent between the emitter terminal and the collector terminal, forexample.

FIG. 14 illustrates an electrosurgical instrument 1200 comprising ahandle end 1205, a shaft, or introducer, 1206, and an end effector, orworking end, 1210. Shaft 1206 can comprise any suitable cross-section,such as a cylindrical and/or rectangular cross-section, for example, andcan comprise a tubular sleeve that extends from handle 1205. Endeffector 1210 can extend from shaft 1206 and may be adapted for weldingand transecting tissue. In various embodiments, end effector 1210 cancomprise an openable and closeable jaw assembly which can, in variousembodiments, comprise straight, curved, and/or any other suitablyconfigured jaws. In various embodiments, the end effector 1210 cancomprise a first jaw 1222A and a second jaw 1222B, wherein at least oneof the jaws 1222A and 1222B can move relative to the other. In at leastone embodiment, the first jaw 1222A can be pivoted about an axisrelative to the second jaw 1222B in order close onto, capture, and/orengage tissue positioned between the jaws and apply a compression forceor pressure thereto. In various embodiments, the handle 1205 cancomprise a lever arm 1228 adapted to actuate a translatable member 1240.More particularly, in at least one embodiment, the lever arm 1228 can beactuated in order to move member 1240 distally toward the distal end1211 of end effector 1210 and, when member 1240 is advanced distally,member 1240 can contact first jaw 1222A and move it downwardly towardsecond jaw 1222B, as illustrated in FIG. 15B. In at least oneembodiment, the translatable member 1240 can comprise a proximal rackportion and the lever arm 1228 can comprise a plurality of gear teethwhich can be configured to drive the proximal rack portion oftranslatable member 1240 distally. In certain embodiments, rotation ofthe lever arm 1228 in the opposite direction can drive the translatablemember 1240 proximally.

As described above, the translatable member 1240 can be configured tocontact first jaw 1222A and pivot jaw 1222A toward second jaw 1222B. Invarious embodiments, referring now to FIGS. 15A-15C, the distal end ofreciprocating member 1240 can comprise a flanged “I”-beam configured toslide within a channel 1242 in the jaws 1222A and 1222B. Referringprimarily to FIG. 15C, the I-beam portion of member 1240 can comprise anupper flange 1250A, a lower flange 1250B, and a center, or intermediate,portion 1251 connecting the flanges 1250A and 1250B. In at least oneembodiment, the flanges 1250A and 1250B and the center portion 1251 candefine “c”-shaped channels on the opposite sides of member 1240. In anyevent, in various embodiments, the flanges 1250A and 1250B can defineinner cam surfaces 1252A and 1252B, respectively, for slidably engagingoutward-facing surfaces 1262A and 1262B of jaws 1222 a and 1222B,respectively. More particularly, the inner cam surface 1252A cancomprise a suitable profile configured to slidably engage the outersurface 1262A of first jaw 1222A and, similarly, the inner cam surface1252B can comprise a suitable profile configured to slidably engage theouter surface 1262B of second jaw 1222 b such that, as translatablemember 1240 is advanced distally, the cam surfaces 1252A and 1252B canco-operate to cam first jaw member 1222A toward second jaw member 1222Band configure the end effector 1240 in a closed configuration. As seenin FIG. 15B, jaws 1222A and 1222B can define a gap, or dimension, Dbetween the first and second electrodes 1265A and 1265B of jaws 1222Aand 1222B, respectively, when they are positioned in a closedconfiguration. In various embodiments, dimension D can equal a distancebetween approximately 0.0005″ to approximately 0.005″, for example, and,in at least one embodiment, between approximately 0.001″ andapproximately 0.002″, for example.

In various embodiments, further to the above, the surgical instrumentcan comprise a first conductor, such as an insulated wire, for example,which can be operably coupled with the first electrode 1265A in firstjaw member 1222A and, in addition, the surgical instrument can furthercomprise a second conductor, such as an insulated wire, for example,which can be operably coupled with the second electrode 1265B in secondjaw member 1222B. In at least one embodiment, referring again to FIG.14, the first and second conductors can extend through shaft 1206between an electrical connector in handle 1205 and the electrodes 1265Aand 1265B in the end effector 1210. In use, the first and secondconductors can be operably coupled to electrical source 1245 andcontroller 1250 by electrical leads in cable 1252 in order for theelectrodes 1265A and 1265B to function as paired bi-polar electrodeswith a positive polarity (+) and a negative polarity (−). Moreparticularly, in at least one embodiment, one of the first and secondelectrodes 1265A and 1265B can be operably coupled with a positive (+)voltage terminal of electrical source 1245 and the other of the firstand second electrodes 1265A and 1265B can be electrically coupled withthe negative voltage (−) terminal of electrical source 1245. Owing tothe opposite polarities of electrodes 1265A and 1265B, current can flowthrough the tissue positioned between the electrodes 1265A and 1265B andheat the tissue to a desired temperature.

The surgical instrument 1200, and the system comprising electricalsource 1245 and controller 1250, for example, may be configured toprovide different electrosurgical energy-delivery operating modes which,in certain embodiments, may depend on the amount, or degree, of jawclosure. In any event, in various circumstances, further to the above,the degree of jaw closure may be represented by the degree of actuationof lever 1228 such as, for example, degrees of actuation A and Billustrated in FIG. 14. Alternatively, the degree of actuation may berepresented by the axial translation of reciprocating member 1240. Invarious circumstances, it may be useful to switch between differentelectrosurgical energy-delivery operating modes depending on the volumeof tissue captured within the end effector of the surgical instrumentand the amount of compression applied to the tissue. For example, theinstrument 1200 may deliver Rf energy in a first operating mode to largevolumes of the captured tissue in order to cause an initial dehydrationof the tissue, wherein the surgical instrument 1200 may thereafterswitch, and/or be switched by controller 1250, for example, to a secondoperating mode which allows for more effective tissue welding. Invarious circumstances, this second operating mode may provide a greateramount or a lesser amount of energy to the tissue and/or adjust themanner or location in which the energy is being supplied to the tissue.Alternatively, when engaging a lesser volume of tissue, for example, thesurgical instrument 1200 and/or accompanying system may deliver Rfenergy in only one operating mode which can be best suited for tissuewelding, for example.

FIGS. 16A and 16B illustrate views of an alternative embodiment of anend effector, i.e., end effector 1280, which can be similar in manyrespects to the end effector 1210 shown in FIGS. 15A-15B. Similar to theabove, the end effector 1280 can comprise first and second conductivebodies, or electrodes, 1285A and 1285B in the respective first andsecond jaws 1222A and 1222B. In addition, the end effector 1280 canfurther comprise additional conductive bodies, such as third and fourthelectrodes 1290A and 1290B, for example, which can be positioned aroundthe perimeters of electrodes 1285A and 1285B, respectively. In at leastone embodiment, the electrodes 1290A and 1290B can be structural,perimeter components of the respective jaws 1222A and 1222B. In certainembodiments, the third electrode 1290A can surround the perimeter offirst electrode 1285A and, similarly, the fourth electrode 1290B cansurround the perimeter of second electrode 1285B. In at least one suchembodiment, the paired arrangement of electrodes 1285A and 1290A can bea minor-image to the paired arrangement of electrodes 1285B and 1290B.In various embodiments, the jaw member 1222A can further comprise atleast one intermediate material 1292 positioned intermediate the firstand third electrodes 1285A and 1290A in the first jaw 1222A. Similarly,the second jaw member 1222B can further comprise an intermediatematerial 1292 positioned intermediate to the second and fourthelectrodes 1285B and 1290B in the second jaw 1222B. The intermediatematerial 1292 may be at least one of an insulator, a positivetemperature coefficient of resistance (PTC) material, and/or a fixedresistive material, for example.

Similar to the above, the surgical instrument can comprise a pluralityof conductors which can operably couple the positive and negativeterminals of current source 1245 with the electrodes 1285A, 1285B,1290A, and 1290B. For example, in at least one embodiment, the surgicalinstrument can comprise a first conductor electrically coupled with thefirst electrode 1285A, a second conductor electrically coupled with thesecond electrode 1285B, a third conductor electrically coupled with thethird electrode 1290A, and a fourth conductor electrically coupled withthe fourth electrode 1290B, wherein the first, second, third, and fourthconductors can be selectively coupled with the positive and/or negativeterminals of electrical source 1245, for example. More particularly, thesurgical instrument can be operated in various modes of operation inwhich one or more of the electrodes 1285A, 1285B, 1290A, and 1290B, viatheir respective conductors, are electrically coupled with the positive(+) terminal of the electrical source 1245 and one or more of theelectrodes 1285A, 1285B, 1290A, and 1290B, via their respectiveconductors, are electrically coupled with the negative (−) terminal ofthe electrical source 1245. In various circumstances, referring to FIGS.16A-19C, the first, second, third, and fourth electrodes 1285A, 1285B,1290A and 1290B are indicated in various modes of operation as havingpolarities indicated as a positive polarity (+), a negative polarity(−), or an absence of polarity (Ø). In some embodiments, thetranslatable member 1240 can carry electrical current or, alternatively,the translatable member 1240 can be coated with an insulator layer toprevent the member 1240 from functioning as a conductive path for thecurrent.

In various embodiments, further to the above, the polarity of theelectrodes 1285A, 1285B, 1290A, and/or 1290B can be switched dependingon the degree of jaw closure. In at least one operating mode, electrodeswithin the same jaw can comprise different polarities. For example, ascan be seen in FIGS. 16A, 16B, and 19A, the polarities of the electrodescan be such that current can flow between electrodes 1285A (+) and 1290A(−) in the first jaw 1222A and, similarly, between electrodes 1285B (+)and 1290B (−) in the second jaw 1222B. In various circumstances, thisoperating mode may be well-suited for sealing or welding thin or highlycompressed tissues volumes. In at least one operating mode, theelectrodes which are positioned opposite each other can have differentpolarities. For example, as can be seen in FIG. 19B, the interiorelectrodes 1285A (−) and 1285B (+) are switched to have opposingpolarities for providing Rf current paths through the tissue positionedbetween the jaws 1222A and 1222B in order to cause dehydration of thicktissue volumes, for example. The second and fourth electrodes 1290A and1290B may also have opposite polarities or, alternatively, they may havea null polarity or an absence of polarity (Ø), as illustrated in FIG.19B, for example. In various circumstances, further to the above, theoperational mode of FIG. 19B may be useful when the jaws are moved froma fully open position, or 0% jaw closure (FIGS. 16A-16B), into anintermediate closure configuration in order to at least partiallydehydrate the tissue. Once in the intermediate closure configuration, asillustrated in FIG. 17, the surgical instrument may switch into theoperational mode of FIG. 19A which may provide a more optimal energydelivery configuration for creating a high-strength seal or weld in theengaged tissue.

In various embodiments, further to the above, a control system and/orcontroller 1250 can switch the surgical instrument from one operatingmode to another mode after the jaw has been closed a predeterminedamount, wherein, in at least one embodiment the switchover can occur at10%, 20%, 30%, 40%, 50%, 60%, 70%, and/or 80% of the jaw closure, forexample. In certain embodiments, the surgical instrument can comprise asensor configured to detect the degree to which first jaw 1222A has beenclosed. In various embodiments, the switching between electrosurgicalmodes can be triggered by one or more operational parameters, such as(i) the degree of jaw closure as described above, (ii) the impedance ofthe engaged tissue, and/or (iii) the rate of change of impedance or anycombination thereof. Furthermore, the polarity of the electrodes can beswitched more than two times during the operation of the surgicalinstrument. Other operating modes are disclosed in U.S. patentapplication Ser. No. 12/050,462, entitled ELECTROSURGICAL INSTRUMENT ANDMETHOD, filed on Mar. 18, 2008, the entire disclosure of which isincorporated by reference herein.

As discussed above, the translatable member 1240 can be at leastpartially advanced in order to move the first jaw 1222A toward thesecond jaw 1222B. Thereafter, the movable member 1240 can be advancedfurther distally in order to transect the tissue positioned between thefirst jaw 1222A and the second jaw 1222B. In certain embodiments, thedistal, or leading, end of the I-beam portion of 1240 can comprise asharp, or knife, edge which can be configured to incise the tissue. Asthe member 1240 is advanced through the tissue, the electrical currentcan be supplied to the electrodes of the first and second jaw members asdescribed above. In certain embodiments, as described above, the cuttingmember 1240 can act as an electrode when it is electrically coupled to apositive terminal or negative terminal of the source 1245, and/or anysuitable ground. In various circumstances, the operation of the trigger1228 can advance the knife edge of the cutting member 1240 to the verydistal end of slot or channel 1242. After the cutting member 1240 hasbeen sufficiently advanced, the trigger 1288 can be released and movedinto its original, or unactuated, position in order to retract thecutting member 1240 and allow first jaw 1222A to move into is openposition again. In at least one such embodiment, the surgical instrumentcan comprise a jaw spring configured to bias the first jaw 1222A intoits open position and, in addition, a trigger spring configured to biasthe trigger 1288 into its unactuated position.

In various embodiments, as described above, current can flow from oneelectrode to another while passing through the tissue captured by theend effector of the surgical instrument. As also described above, thecurrent passing through the tissue can heat the tissue. In variouscircumstances, however, the tissue may become overheated. In order toavoid such overheating, the electrodes of various surgical instrumentscan comprise materials which may no longer conduct current, or mayconduct at least substantially less current, when the electrodematerials have reached or exceeded a certain temperature. Stated anotherway, in at least one embodiment, the electrical resistance of theelectrode material can increase with the temperature of the materialand, in certain embodiments, the electrical resistance of the materialcan increase significantly when the material has reached or exceeded acertain transition, or switching, temperature. In various circumstances,such materials can be referred to as positive temperature coefficient,or PTC, materials. In at least some such PTC materials, the PTC materialcan be comprised of a first non-conductive material, or substrate, whichhas a high electrical resistance and, in addition, a second, conductivematerial, or particles, having a lower electrical resistanceinterdispersed throughout the substrate material. In at least oneembodiment, the substrate material can comprise polyethylene and/orhigh-density polyethylene (HDPE), for example, and the conductivematerial can comprise carbon particles, for example. In any event, whenthe temperature of the PTC material is below its transition temperature,the conductive material can be present in the non-conductive material ina sufficient volumetric density such that the current can flow throughthe PTC material via the conductive particles. When the temperature ofthe PTC material has exceeded its transition temperature, the substrate,or non-conductive material may have sufficiently expanded and/or changedstates such that the conductive particles are no longer sufficiently incontact with one another in order provide a sufficient path for thecurrent to flow therethrough. Stated another way, the expansion and/orstate change of the substrate material may cause the volumetric densityof the conductive particles to fall below a sufficient volumetricdensity in order for current to be conducted therethrough, or at leastsubstantially conducted therethrough. In various circumstances, as aresult of the above, the PTC material may act as a circuit breaker whichcan prevent, or at least inhibit, additional energy from reaching thetissue being treated, that is, at least until the PTC material hascooled sufficiently and reached a temperature which is below thetransition, or switching, temperature. At such point, the PTC materialcould begin to conduct current again.

Further to the above, describing a material as having a positivetemperature coefficient of resistance (PTC) can mean that the resistanceof the material increases as the temperature of the material increases.Many metal-like materials exhibit electrical conduction that has aslight positive temperature coefficient of resistance. In suchmetal-like materials, the PTC's variable resistance effect ischaracterized by a gradual increase in resistance that is linearlyproportional to temperature—that is, a linear PTC effect. A “nonlinear”PTC effect can be exhibited by certain types of polymer matrices, orsubstrates, that are doped with conductive particles. These polymer PTCcompositions can comprise a base polymer that undergoes a phase changeor can comprise a glass transition temperature Tg such that the PTCcomposition has a resistance that increases sharply over a narrowtemperature range (see FIG. 9).

Polymeric PTC material can consist of a crystalline or semi-crystallinepolymer (e.g., polyethylene) that carries a dispersed filler ofconductive particles, such as carbon powder or nickel particles, forexample, therein. In use, a polymeric PTC material can exhibittemperature-induced changes in the base polymer in order to alter theelectrical resistance of the polymer-particle composite. In a lowtemperature state, the crystalline structure of the base polymer cancause dense packing of the conductive particles (i.e., carbon) into itscrystalline boundaries so that the particles are in close proximity andallow current to flow through the PTC material via these carbon“chains”. When the PTC material is at a low temperature, numerous carbonchains form the conductive paths through the material. When the PTCmaterial is heated to a selected level, or an over-current causes I²Rheating (Joule heating) within the PTC material, the polymer basematerial may be elevated in temperature until it exceeds a phasetransformation temperature. As the polymer passes through this phasetransformation temperature, the crystalline structure can change to anamorphous state. The amorphous state can cause the conductive particlesto move apart from each other until the carbon chains are disrupted andcan no longer conduct current. Thus, the resistance of the PTC materialincreases sharply. In general, the temperature at which the base polymertransitions to its amorphous state and affects conductivity is calledits switching temperature Ts. In at least one embodiment, the transitionor switching temperature Ts can be approximately 120 degrees Celsius,for example. In any event, as long as the base polymer of the PTCmaterial stays above its switching temperature Ts, whether from externalheating or from an overcurrent, the high resistance state will remain.Reversing the phase transformation allows the conductive particle chainsto reform as the polymer re-crystallizes to thereby restore multiplecurrent paths, and a low resistance, through the PTC material.Conductive polymer PTC compositions and their use are disclosed in U.S.Pat. Nos. 4,237,441; 4,304,987; 4,545,926; 4,849,133; 4,910,389;5,106,538; and 5,880,668, the entire disclosures of which areincorporated by reference herein.

As discussed above, in many embodiments, the conductive polymer PTCcomposition may comprise a base polymer, or substrate, and conductiveelements dispersed in the base polymer. When describing properties ofthe base polymer of a PTC composition, it may be useful to furtherexplain the terms glass transition temperature Tg and meltingtemperature Tm. A glass transition temperature Tg of a material may notbe the same as a melting temperature Tm. A transition at Tm occurs incrystalline polymers when the polymer chains fall out of theircrystalline phase, and become a disordered deformable or flowable media.A glass transition at Tg is a transition which occurs in amorphouspolymers (i.e., polymers whose chains are not arranged in orderedcrystals). A glass transition temperature (Tg) in a crystalline polymermay be defined as a temperature point where the polymer experiences asignificant change in properties—such as a large change in Young'smodulus (also known as modulus of elasticity), for example. In suchcircumstances, the Tg can comprise the temperature at which the polymerstructure turns “rubbery” upon heating and “glassy” upon cooling.Crystalline polymers may also go through a stage of becoming leatherybefore becoming rubbery. There is a loss of stiffness (e.g., decreasedmodulus of elasticity) in both of these stages. Such crystallinepolymers, or domains thereof, can comprise a sharp, defined meltingpoint Tm. In contrast, an amorphous polymer can be structural below theglass transition temperature Tg and transition from being stiff toflowable (at its melting temperature Tm) over a wide temperature range.

The temperature-induced variable resistance of a polymer PTC compositionwhen used in a current-limiting application can be based on an overallenergy balance—and can be described by Equation (1) below. It may now beuseful to describe the basic thermal/resistance properties of a PTCdevice comprising a polymeric PTC composition to explain how (i) highlynon-linear PTC effects and (ii) rapid switching may be achieved in thePTC materials described herein.

m*Cp(ΔT/Δt)=I ² *R−U*(T−Ta)—  Equation (1), wherein:

m=mass of the PTC composition

Cp=specific heat capacity of the PTC composition (at a constantpressure)

ΔT=change in temperature of the PTC composition

Δt=change in time

I=current flowing through the PTC composition

R=resistance of the PTC composition

U=overall heat-transfer coefficient

T=temperature of the PTC composition

Ta=ambient temperature

In equation (1) above, the current flowing through the PTC compositiongenerates heat at a rate equal to I²R. All or some of this heat can besubtracted by interaction with the environment at a rate described bythe term U*(T−Ta), depending on how the device or composition isconfigured for interaction with the environment. This portion ofequation (1), i.e., U*(T−Ta), accounts for losses due to one or more ofconvection, conduction, and radiation heat transfers. Any heat notsubtracted by environmental interaction raises the temperature of thePTC composition/device at a rate described by the term:m*Cp*(ΔT/Δt)—Equation (2). The reader will note that Equation (2)assumes that there is a uniform temperature across the polymeric PTCcomposition. In circumstances where this is not true, this portion ofthe equation can be adapted in order to account for suchparticularities. In any event, if the heat generated by the polymericPTC composition and the heat subtracted to the operating environment arein balance, T/t goes to zero, and Equation (1) can be rewritten as:I²*R−U*(T−Ta)—Equation (3). In various circumstances, under certainoperating conditions, the heat generated within the PTC material and theheat lost by the PTC material to the environment can be in balance at arelatively low temperature such as, for example, Point A shown in FIG.9. If the current flow (I) through the PTC composition increases and theambient temperature remains constant, the heat generated by the PTCcomposition increases and, correspondingly, the temperature of the PTCcomposition also increases. In the event, however, that the increase incurrent is not too large and all the generated heat can be lost to theenvironment, the temperature and resistance of the PTC material maystabilize according to Equation (3) at a higher temperature, such asPoint B in FIG. 9, for example.

In various circumstances, if the ambient temperature surrounding the PTCmaterial, or the temperature of an object engaged by the PTC material,increases instead of the current, the PTC material may stabilizeaccording to Equation (3) at a slightly higher temperature (possiblyagain at Point B in FIG. 9). Point B in FIG. 9 can also be reached as aresult of an increase in current (I) and an increase in ambienttemperature Ta. In various circumstances, however, further increases ineither or both of these conditions may cause the PTC material to reach atemperature Ts at which the resistance rapidly increases (e.g., fromPoint B to Point C in FIG. 9). At this stage, large increases inresistance occur with small changes in temperature. In FIG. 9, thisoccurs between Points B and C, and this vertical or “square” portion ofthe curve defines the operating region of the PTC composition in itstripped state. The large change in resistance causes a correspondingdecrease in current flow in a circuit including or otherwiseelectrically coupled to the PTC composition. In various circumstances,the resistance, or impedance, can increase by approximately two ordersof magnitude, for example, while, in other circumstances, theresistance, or impedance, can increase by approximately four orders ofmagnitude, for example. In certain circumstances, the change in theresistance, or impedance, can depend on the frequency of the currentpassing through the PTC material. In at least some circumstances, theresistance can increase by four orders of magnitude when the current isat Rf frequencies, for example, and two orders of magnitude when thecurrent is below Rf frequencies, for example. In any event, because thetemperature change between Points B and C in FIG. 9 is very small, theterm (T−Ta) in Equation (3) can be replaced by the constant (Ts−Ta),wherein Ts is the current-limiting, or switching, temperature of thedevice. As a result of the above, Equation (1) can be rewritten as:I²*R=V²/R=U*(Ts−Ta)—Equation (4). Because U and (Ts−Ta) are now bothconstants, Equation (4) reduces to I²R=constant; that is, the device nowoperates in a constant power state under these conditions. Expressingthis constant power as V²/R emphasizes that, in the tripped state, theresistance of the PTC material is proportional to the square of theapplied voltage. This relation holds until the composition/deviceresistance reaches the upper “square” region of the curve (Point C inFIG. 9).

For a PTC composition that has tripped, i.e., exceed its switchtemperature, the PTC composition will remain in the tripped state andwill remain substantially non-conductive as long as the applied voltageis high enough for the resulting V²/R to supply and/or exceed theU(Ts−Ta) loss. When the voltage is decreased to the point at which theU(Ts−Ta) loss can no longer be supplied to the PTC material, the PTCmaterial will “reset” or return to its quiescent base resistance, suchas points represented by Points A and/or B, for example. Variousembodiments can comprise PTC materials that allow for a very rapidbi-directional switching (e.g., a small Δt) between Points B and C alongthe resistance-temperature curve of FIG. 9. Various embodiments cancomprise PTC materials that exhibit a resistance-temperature curve witha high degree of “squareness” at its Ts (see FIG. 9), that is, theembodiment of the PTC material will plot an exceedingly rapid nonlinearPTC effect (e.g., a rapid increase in resistivity) in the range of aselected switching temperature Ts. A vertical, or an at leastsubstantially vertical, curve at Ts can mean that the change from a basequiescent resistance to a maximum current-limiting resistance occursover a very small temperature range.

From the following equation, it can be understood that switching timecan be effectively reduced by altering the mass of the PTC composition.The switching time can generally be represented by Equation (5):Δt=m*Cp*(Ts−Ta)/(I²*R). By controlling one or more variables fromEquation (5), various embodiments of PTC materials can provide one orboth of reduced switching time and/or a square resistance-temperaturecurve. An exemplary embodiment of a conductive polymercomposition/polymer composite which provides a greatly increasedswitching speed can utilize thermally insulative, low mass, yetelectrically conductive dispersed nanospheres and/or microspheres. Ithas also been found that the embodiments of the above described polymercomposite can provide a very low or minimum resistance in its initialquiescent state. At the same time, a polymer with thermally insulative,low mass conductive particles can provide for an increased Imaxproperty, i.e., the maximum current the PTC composition can withstandwithout damage. As schematically depicted in FIG. 20, variousembodiments of conductive polymer compositions exhibiting PTC propertiescan comprise a PTC composite 99 comprising a polymer matrix 100including a polymer base material 102 with dispersed conductive elementswhich, in various embodiments, can have low densities and correspondinglow thermal conductivity properties. In at least one embodiment, anexemplary polymeric PTC composite can utilize core-shell particlescomprising a core 105 having a very low mass and very low thermalconductivity, such as microspheres and/or nanospheres having a nanoscaleconductive coating indicated at 110. In one embodiment, referring toFIG. 20, the core 105 of the conductive dispersed elements can compriseglass microspheres with a hollow portion 112, but solid and/or porousglass microspheres or filaments could be used in addition to or in lieuof the above, for example.

In various embodiments, referring now to FIG. 21, a jaw 1122A of an endeffector of an electrosurgical instrument can include a first electrode1180A comprised of a first positive temperature coefficient (PTC)material and, in addition, a second electrode 1180B comprised of asecond PTC material. The first electrode 1180A can comprise a first side1184, a second side 1185 positioned opposite the first side 1184, and adistal end 1186 portion connecting the first and second sides. Thesecond electrode 1180B can, similarly, comprise a first side 1187positioned adjacent to the first side 1184 of the first electrode 1180A,a second side 1188 positioned adjacent to the second side 1185 of thefirst electrode 1180A, and a distal end portion 1189 connecting thefirst and second sides of the second electrode 1180B. As illustrated inFIG. 21, the second electrode 1180B is positioned around the perimeterof the first electrode 1180A such that the second electrode 1180Bsurrounds the first electrode 1180A. Referring now to FIGS. 21 and 22,the jaw 1122 a can comprise a substantially U-shaped channel comprisingan outer sidewall 1170, an inner sidewall 1172, and a base 1171connecting the sidewalls 1170 and 1172, wherein the sidewalls 1170 and1172 can define a gap therebetween configured to receive electrodes1180A and 1180B securely therein. In certain embodiments, the electrodes1180A and 1180B can be press-fit into the gap intermediate sidewalls1170 and 1172 and/or secured into place using fasteners, for example. Inat least one embodiment, the sidewalls of the first, or inner, electrode1180A can be in abutting contact with the sidewalls of the second, orouter, electrode 1180B. In certain other embodiments, an insulativematerial can be positioned intermediate the first and second electrodes1180A and 1180B. In various embodiments, the jaw 1122 a can furthercomprise insulative material positioned intermediate the electrodes1180A and 1180B and the sidewalls 1170 and 1172, respectively, while, inother embodiments, the electrodes 1180A and 1180B can be in abuttingcontact with the sidewalls 1170 and 1172. Similarly, in at least oneembodiment, the jaw 1122A can further comprise an insulative materialpositioned intermediate the electrodes 1180A and 1180B and the base 1171while, in other embodiments, the electrodes 1180A and 1180B can be inabutting contact with the base 1171.

In various embodiments, further to the above, a second jaw of theelectrosurgical instrument can comprise an opposing electrode 1181positioned opposite the first and second electrodes 1180A and 1180B. Inuse, referring again to FIG. 22, tissue “T” can be captured intermediatethe first jaw 1122A and the second jaw 1122B of the electrosurgicalinstrument such that the tissue T is compressed between the electrodes1180A, 1180B and the return electrode 1181. As discussed above, avoltage differential can be generated between the electrode 1180A andthe opposing electrode 1181 and, similarly, between the electrode 1180Band the opposing electrode 1181 such that current can flow between theelectrodes and through the tissue T. An electrical schematic of thisarrangement is depicted in FIG. 23 wherein the first electrode 1180A andthe second electrode 1180B are part of parallel circuits electricallycoupled with the RF source 1245. More particularly, the first electrode1180A is part of a first circuit comprising electrode 1180A, tissue T,and opposing electrode 1181 wherein each of these elements can compriseresistive, and/or capacitive, properties. With regard to this firstcircuit, the first electrode 1180A is electrically coupled to thenegative terminal of the RF source 1245 and the opposing electrode 1181is electrically coupled to the positive terminal of the RF source 1245,although the reverse arrangement may be possible. Similarly, the secondelectrode 1180B is part of a second circuit comprising second electrode1180B, tissue T, and opposing electrode 1181 wherein each of theseelements can comprise resistive, and/or capacitive, properties. Withregard to this second circuit, the second electrode 1180B iselectrically coupled to the negative terminal of the RF source 1245 andthe opposing electrode 1181 is electrically coupled to the positiveterminal of the RF source 1245, although the reverse arrangement may bepossible.

As discussed above, the first electrode 1180A can be comprised of afirst PTC material and the second electrode 1180B can be comprised of asecond PTC material. In various embodiments, the first PTC material cancomprise a first switching temperature while the second PTC material cancomprise a second switching temperature. In various embodiments, thefirst and second switching temperatures can be between approximately 80degrees Celsius and approximately 150 degrees Celsius, for example. Incertain embodiments, the first and second switching temperatures can bea function of the clamping pressure applied to the tissue by the firstand second jaws, as described in greater detail below. In variouscircumstances, the switching temperature can be inversely proportionalto the clamping pressure, i.e., the switching temperature may be lowerfor higher clamping pressures, for example. In any event, when the firstand second PTC materials are below their switching temperatures, thefirst and second electrodes 1180A and 1180B can both have an electricalresistance which permits sufficient current, i.e., current sufficient totherapeutically treat and/or irreversibly alter the tissue beingtreated, to be conducted through the electrodes 1180A and 1180B and thetissue T. As discussed above, the flow of current through the electrodes1180A, 1180B, tissue T, and the opposing electrode 181 can generate heatwithin the tissue and electrodes 1180A and 1180B and, as a result, causethe temperature of the PTC materials to rise. In various embodiments,the first PTC material of first electrode 1180A can have a firstswitching temperature which is higher than the second switchingtemperature of the second PTC material of second electrode 1180Bwherein, as a result, the second electrode 1180B can “shut-off” or“switch-off” before the first electrode 1180A. Stated another way, thesecond electrode 1180B can reach its switching temperature before thefirst electrode 1180A reaches its switching temperature and, once thesecond electrode 1180B has reached its switching temperature, theelectrical resistance of the second electrode 1180B can increasesignificantly, as outlined above. In such circumstances, the flow ofcurrent through the tissue T can be substantially limited to a flow ofcurrent between the first electrode 1180A and the opposing electrode1181 at least until the first PTC material of the first electrode 1180Areaches its switching temperature and the electrical resistance of thefirst electrode 1180A increases significantly. In various circumstances,an electrical resistance can increase significantly when it increases bya factor of approximately 2, 4, 10, 100, and/or 1000, for example, at aspecific switching temperature and/or at a switching temperaturecomprising a narrow transition range of temperatures.

In various circumstances, referring now to FIG. 24, thetemperature-resistance relationship of the first PTC material of thefirst electrode 1180A can be plotted by the curve 1182A and thetemperature-resistance relationship of the second PTC material of thesecond electrode 1180B can be plotted by the curve 1182B. As illustratedin FIG. 24, the curves 1182A and 1182B depict that that the first PTCmaterial has a first, or initial, electrical resistance which is lowerthan first, or initial, electrical resistance of the second PTCmaterial. Alternatively, although not depicted, the first, or initial,electrical resistance of the second PTC material can be lower than thefirst, or initial, electrical resistance of the first PTC material. Inany event, the curves 1182A and 1182B also depict that the resistance ofthe first PTC material can increase significantly from Points B to C toa second electrical resistance at the switching temperature TsA while,at the same temperature, the resistance of the second PTC material cancontinue to increase incrementally between points D and E. Once theswitching temperature TsB (point E) is reached, the resistance of thesecond PTC material can increase significantly from points E to F while,at the same temperature, the switched resistance of the first PTCmaterial only increases incrementally. Any additional increase intemperature, as depicted by curves 1182A and 1182B, may only result inincremental increases of the switched resistances of the first andsecond PTC materials. As the reader will note, the switched resistanceof the second PTC material is larger than the switched resistance of thefirst PTC material after both the materials have exceeded theirswitching temperatures. Alternatively, although not depicted, theswitched electrical resistance of the second PTC material can be lowerthan the switched electrical resistance of the first PTC material.

In various embodiments, referring again to FIG. 22, the end effector ofthe electrosurgical instrument can comprise a central axis 1125, alongwhich a cutting slot 1142 can be defined, wherein the cutting slot 1142can be configured to slidably receive a cutting member, or knife,therein. Further to the above, the first electrode 1180A can bepositioned closer to the central axis of the end effector than thesecond electrode 1180B and, as the switching temperature of the secondPTC material is lower than the switching temperature of the first PTCmaterial, the second, or outer, electrode 1180B may stop conductingcurrent, or at least substantially stop conducting current, before thefirst, or inner, electrode 1180A stops, or at least substantially stops,conducting current. In such circumstances, the current, and the heatbeing generated by the current, may be centralized in the end effectornear the central axis of the end effector as opposed to the outerperiphery of the end effector and, as a result, the lateral spread ofheat from the end effector into the adjacent tissue may be reduced. Incertain embodiments, the jaws of the end effector can further compriseone or more materials 1173 extending around at least a portion of theperimeter of the jaws, wherein the materials 1173 can be configured toreduce the lateral, or outward, spread of heat from the end effector. Inat least one such embodiment, the materials 1173 can be comprised of atleast one high resistance material which can restrict, or at leastsubstantially restrict, the flow of current therethrough. Moreparticularly, the sidewalls 1170, 1172 and base 1171 can, in certaincircumstances, comprise a return path for the current flowing throughthe tissue T, wherein, in the event that the sidewalls 1170, 1172 andbase 1171 comprise a high resistance material 1173, the flow of currentthrough the outer surfaces, or outer portions, of the jaws can bereduced. As a result, the flow of current, or current density, betweenthe first and second jaws may be more centralized toward the inside, ormiddle, of the jaws as opposed to the outside of the jaws and,accordingly, the lateral or outward spread of heat from the jaws can bereduced. In certain embodiments, the high resistance materials 1173 canbe embedded in sidewalls 1170, 1172 and/or base 1171 while, in someembodiments, the materials comprising the sidewalls 1170, 1172 and/orbase 1171 can be comprised of a high resistance material. In certainembodiments, the material 1173 and/or any other outer portions of thejaws can be comprised of one or more PTC materials. In at least one suchembodiment, the PTC materials can comprise a switching temperature whichis lower than the switching temperature of the PTC materials in theelectrodes, for example.

In various embodiments, referring now to FIGS. 28-33, an end effector ofa surgical instrument, such as end effector 1410, for example, cancomprise a first jaw 1422A and a second jaw 1422B, wherein at least oneof the jaws 1422A, 1422B can comprise, further to the above, one or moreinserts positioned within one or more channels and/or slots in the jaws1422A, 1422B, for example. In at least one embodiment, the first jaw1422A can comprise at least one slot 1423 which can be configured toreceive an insert 1424A. The insert 1424A can comprise a circular, or atleast substantially circular, retention head 1425 which can beconfigured to be retained in a circular, or at least substantiallycircular, portion of slot 1423. In various embodiments, the insert 1424Acan further comprise an outer portion 1426A which can comprise an outerprofile which can be flush, or at least substantially flush, with theouter profile 1427A of the first jaw 1422A, for example. Similar to theabove, the second jaw 1422B can also comprise at least one slot 1423which can be configured to receive an insert 1424B. Also similar to theabove, the outer portion 1426B of the insert 1424B can be flush, or atleast substantially flush, with the outer profile 1427B of the secondjaw 1422B. In various embodiments, further to the above, the inserts1424A and/or 1424B, for example, can be comprised of a material havingan electrical resistance which is higher than the electrical resistanceof the frame portions 1428A and 1428B of jaws 1422A and 1422B,respectively. Owing to the higher resistances in the inserts 1424A and1424B, during use, the density of current that may flow through thetissue and into the outer portions of the jaw members 1422A and 1422Bcan be reduced. In various embodiments, further to the above, theinserts 1424A and/or 1424B can be comprised of a positive temperaturecoefficient (PTC) material which can have, at least initially, asufficiently low resistance to allow a high density of current to flowfrom the electrodes 1480 and/or 1481, for example, into the outerportions of jaws 1422A and 1422B. Once the temperature of these PTCmaterials have exceeded their switching temperatures, however, theelectrical resistances of the PTC materials can increase significantlysuch that the flow of current through the inserts 1424A and 1424B andthe outer portions of the jaws 1422A and 1422B can be stopped, or atleast significantly reduced. In certain embodiments, a PTC material canbe coated onto the outside of at least one of the jaws 1422A and 1422B,for example. In at least one such embodiment, a PTC material could beapplied to the jaw frames 1428A and 1428B from a solvent solution and/orfrom a two phase system, for example. In at least one embodiment, asolvent solution can comprise carbon black particles suspended in asolution comprising alcohol and/or an air-curable adhesive, for example.In certain embodiments, a two phase system can comprise a latex paint, asolvent, insoluble polymer micelles, and/or suspended particles, such ascarbon, for example. In at least one embodiment, an insulating coatingcould be sprayed onto the jaw frames 1428A and 1428B, for example,regardless of whether the coating includes a switching temperatureproperty.

In various embodiments, referring now to FIG. 25, an end effector, suchas end effector 1310, for example, can comprise more than two electrodescomprised of PTC materials having different switching temperatures. Inat least one embodiment, the end effector 1310 can comprise a first jaw1322A and a second jaw 1322B wherein the first jaw 1322A, for example,can comprise a first electrode 1380A comprised of a first PTC materialhaving a first switching temperature, a second electrode 1380B comprisedof a second PTC material having a second switching temperature, and athird electrode 1380C comprised of a third PTC material having a thirdswitching temperature. Similar to electrodes 1180A and 1180B, electrodes1380A, 1380B, and/or 1380C can comprise substantially U-shapedelectrodes having opposing first and second sides as illustrated in FIG.25. In at least one embodiment, the electrodes 1380A, 1380B, and 1380Ccan be separated from one another by air gaps and/or insulativematerials, for example. In any event, similar to the above, the secondjaw 1322B can comprise an opposing electrode 1381 which can bepositioned opposite the electrodes 1380A, 1380B, and 1380C such that, inuse, current can flow between the electrodes and the tissue positionedtherebetween. In certain embodiments, referring again to FIG. 25, thesecond jaw 1322B can further comprise an insulator 1382 which can beconfigured to electrically insulate the opposing electrode 1381 from theouter jaw portion, or frame, 1328B of second jaw 1322B. An electricalschematic of the above-described arrangement is depicted in FIG. 26wherein the first electrode 1380A, the second electrode 1380B, and thethird electrode 1380C are part of parallel circuits electrically coupledwith the RF source 1245. More particularly, the first electrode 1380A ispart of a first circuit comprising electrode 1380A, tissue T, andopposing electrode 1381 which can all comprise resistive, and/orcapacitive, properties. With regard to this first circuit, the firstelectrode 1380A is electrically coupled to the negative terminal of theRF source 1245 and the opposing electrode 1381 is electrically coupledto the positive terminal of the RF source 1245, although the reversearrangement may be possible. Similarly, the second electrode 1380B ispart of a second circuit comprising second electrode 1380B, tissue T,and opposing electrode 1381 which can all comprise resistive, and/orcapacitive, properties. With regard to this second circuit, the secondelectrode 1380B is electrically coupled to the negative terminal of theRF source 1245 and the opposing electrode 1381 is electrically coupledto the positive terminal of the RF source 1245, although the reversearrangement may be possible. Similarly, the third electrode 1380C ispart of a third circuit comprising third electrode 1380C, tissue T, andopposing electrode 1381 which can all comprise resistive, and/orcapacitive, properties. With regard to this third circuit, the thirdelectrode 1380C is electrically coupled to the negative terminal of theRF source 1245 and the opposing electrode 1381 is electrically coupledto the positive terminal of the RF source 1245, although the reversearrangement may be possible.

In various embodiments, further to the above, the second switchingtemperature of the second PTC material (electrode 1380B) can be lowerthan the first switching temperature of the first PTC material(electrode 1380A) and the third switching temperature of the third PTCmaterial (electrode 1380C) can be lower than the second switchingtemperature of the second PTC material. In various circumstances, alsofurther to the above, the current flowing through the electrodes and thetissue can cause the temperature of the electrodes 1380A, 1380B, and1380C to increase, wherein the switching temperature of the third PTCmaterial of the third electrode 1380C can be exceeded before theswitching temperatures of the PTC materials of the electrodes 1380A and1380B. In such circumstances, the resistance of the third, or outer,electrode 1380C can increase significantly such that the current, or atleast a substantial portion of the current, flowing between the firstand second jaws flows between the electrodes 1380B, 1380A and theopposing electrode 1381. As the temperature of the tissue and theelectrodes continue to increase, the switching temperature of the secondPTC material of second electrode 1380B can be exceeded followed by theswitching temperature of the first PTC material of first electrode1380A. Similar to the above, the resistance of the second, or middle,electrode 1380B can increase significantly when its switchingtemperature is exceeded such that the current, or at least a substantialportion of the current, flowing between the first and second jaws flowsbetween the first, or inner, electrode 1380A and the opposing electrode1381, wherein, after the switching temperature of the first PTC materialhas been exceeded, the current flowing between the first and second jaws1322A, 1322B can be stopped, or at least substantially stopped. Invarious embodiments, as a result of the above, the outer electrodes ofthe end effector can be “switched off” before the inner electrodes,although other embodiments are envisioned in which the electrodes can becomprised of suitable PTC materials which can allow the electrodes to“switch off” in any suitable order. In certain embodiments, theelectrodes comprising PTC materials having the highest switchingtemperature can be positioned outwardly in relation to electrodescomprising PTC materials having a lower switching temperature, forexample.

In various embodiments, further to the above, the first jaw 1322A can bemoved from an open position into a closed position relative to thesecond jaw 1322B wherein, at such point, a voltage potential can beapplied simultaneously to the electrodes 1380A, 1380B, and/or 1380C suchthat current flows through the tissue positioned intermediate the firstand second jaws 1322A, 1322B. Alternatively, upon closing the first jaw1322A, a voltage potential may be applied sequentially to the electrodes1380A, 1380B, and 1380C. In at least one such embodiment, a voltagepotential may first be applied to the first electrode 380A in order tobegin the sealing process of the tissue in the center of the endeffector. Thereafter, a voltage potential may be applied to the secondelectrode 1380B in order further seal the tissue. In variousembodiments, the voltage potential applied to the second electrode 1380Bcan be applied during and/or after the period of time in which thevoltage potential is applied to the first electrode 1380A. In certainembodiments, the electrosurgical instrument can comprise a computer, orcontroller, such as a microprocessor, for example, which can comprise atimer circuit configured to apply the voltage potential to the firstelectrode for a first period of time and, similarly, apply the voltagepotential to the second electrode for a second period of time. Incertain embodiments, the electrosurgical instrument can further comprisea sensor, for example, operably coupled with the computer which can beconfigured to detect the advancement of the cutting member through theend effector and, upon sensing the advancement of the cutting member,the computer can apply the voltage potential to the second electrode1380B, reduce the voltage potential being applied to the first electrode1380A, and/or stop applying the voltage potential to the first electrode1380A altogether, for example. After a certain period of time and/orafter the sensor has detected a predetermined amount of movement of thecutting member, the computer can apply a voltage potential to the thirdelectrode 1380C, reduce the voltage potential being applied to the firstelectrode 1380A and/or second electrode 1380B, and/or stop applying thevoltage potential to the first electrode 1380A and/or second electrode1380B altogether, for example. In certain embodiments, the computer canbe configured to evaluate the current passing through the electrodes1380A, 1380B, and/or 1380C and/or evaluate the electrical resistances ofthe electrodes 1380A, 1380B, and/or 1380C in order to determine whetherthe switching temperatures of the PTC materials have been reached. In atleast one embodiment, upon detecting that the switching temperature ofthe first PTC material of the first electrode 1380A has been reached,the computer can apply a voltage potential to the second electrode 1380Band, after detecting that the switching temperature of the second PTCmaterial of second electrode 1380B has been reached, apply a voltagepotential to the third electrode 1380C, for example.

In various embodiments, referring now to FIG. 27, an end effector, suchas end effector 1510, for example, can comprise a first jaw 1522A and asecond jaw 1522B wherein the first jaw 1522A can comprise an electrode1580 comprised of a PTC material. The second jaw 1522B can comprise afirst electrode 1581A and a second electrode 1581B wherein, similar toelectrodes 1180A and 1180B, the electrodes 1581A and 1581B can comprisesubstantially U-shaped electrodes having opposing first and secondsides. In at least one embodiment, the electrodes 1581A and 1581B can beelectrically insulated from one another, and/or from the frame 1528B,for example, by one or more insulators, such as insulator 1582, forexample. Also similar to the above, the electrode 1580 can be positionedopposite the electrodes 1581A and 1581B when the first jaw 1522A ispositioned in its closed position opposite the second jaw 1522B suchthat, in use, current can flow between the electrodes and the tissuepositioned therebetween. In various embodiments, the electrodes 1581Aand 1581B may be comprised of a conductive material and can beselectively coupled with the positive terminal of a power source, forexample, while the electrode 1580 can be coupled with the negativeterminal, or ground, of the power source, for example. In addition tothe above, the cutting member 1540 and the frames 1528A, 1528B of jaws1522A, 1522B, respectively, can also be operably coupled to the negativeterminal, or ground, of the power source. During use, in at least onesuch embodiment, current can flow from the electrodes 1581A and 1581B,through the tissue positioned intermediate the jaws 1522A and 1522B, andinto at least one of the PTC electrode 1580, the first frame 1528A, thesecond frame 1528B, and/or the cutting member 1540. In variouscircumstances, a substantial proportion of the current may flow into theopposing PTC electrode 1580, at least when the PTC electrode 1580 isbelow its switching temperature, wherein smaller proportions of thecurrent may flow into the frames 1528A, 1528B and/or cutting member1540. When the PTC electrode 1580 has exceeded its switchingtemperature, the density of current between the electrodes 1581A, 1581Band 1580 can be substantially reduced owing to the substantiallyincreased electrical resistance of the PTC electrode 1580.

In various embodiments, further to the above, an electrosurgicalinstrument comprising end effector 1510 can further comprise a computer,or controller, such as a microprocessor, for example, which canelectrically couple the first electrode 1581A and the second electrode1581B with the positive terminal of a power source, for example, at thesame time such that current can flow between the first electrode 1581Aand the PTC electrode 1580 and between the second electrode 1581B andthe PTC electrode 1580 simultaneously. In various circumstances, thetissue positioned intermediate the first electrode 1581A and the PTCelectrode 1580 can contract, or shrink, due to the thermal effectscaused by the current flowing through the tissue while, similarly, thetissue positioned intermediate the second electrode 1581B and the PTCelectrode 1580 can contract, or shrink, due to the thermal effectscaused by the current flowing through the tissue. In variouscircumstances, the tissue can shrink when it has reached a temperaturebetween approximately 60 degrees Celsius and approximately 70 degreesCelsius, for example. In various embodiments, the computer cansequentially couple the electrodes 1581A and 1581B with the powersource. In at least one such embodiment, the computer can firstelectrically couple the first electrode 1581A with the power source suchthat current can flow between the first electrode 1581A and the PTCelectrode 1580 and cause the tissue positioned therebetween to shrink Insuch circumstances, the shrinking tissue can pull, or apply tension to,the surrounding tissue and, in some circumstances, pull additionaltissue into the end effector. With such additional tissue in the endeffector, in some circumstances, a better seal, or weld, can be createdwithin the tissue.

When the first electrode 1581A is electrically coupled to the powersource, further to the above, the second electrode 1581B can beelectrically uncoupled to the power source. In at least one embodiment,the computer can utilize the second electrode 1581B to monitor theimpedance of the tissue while the tissue between the first electrode1581A and the PTC electrode is welded. In at least one such embodiment,the circuit comprising the second electrode 1581B, the tissue, and areturn path of the current can be utilized to monitor changes in theimpedance and, when changes in the impedance have stopped, or theimpedance begins to approach an asymptote, the amount of tissue stretchor pull that can be created by the operation of first electrode 1581Amay have reached, or at least nearly reached, its maximum. In variouscircumstances, the computer of the electrosurgical instrument can thenapply a voltage potential to the second electrode 1581B. In suchcircumstance, the computer can continue to apply the voltage potentialto the first electrode 1581A or, alternatively, discontinue applying thevoltage potential to the first electrode 1581A. In either event, thetissue positioned intermediate the second electrode 1581B and the PTCelectrode can shrink which can, as a result, pull, or apply tension to,the surrounding tissue and pull additional tissue into the end effector1510. In circumstances where the first electrode 1581A is no longerbeing used to weld the tissue, the circuit comprising first electrode1581A, the tissue, and a return path can be utilized, similar to theabove, to monitor the impedance of the tissue. In any event, any othersuitable operation sequence of the electrodes 1581A and 1581B can beutilized to achieve a desired result. In at least one embodiment, thesecond electrode 1581B can be utilized to seal the tissue before thefirst electrode 1581A is used to seal the tissue. In at least one suchembodiment, the welded tissue between the second electrode 1581B and thePTC electrode 1580 can entrap, or at least partially entrap, the currentand/or heat generated by the first electrode 1581A, when it is operated,within the end effector.

In various embodiments, the cutting member 1540 can be advanced withinthe end effector 1510 at any suitable time during the above-describedsequence. In certain embodiments, the cutting member 1540 can beadvanced when the first electrode 1581A is polarized and being used toweld tissue and before the second electrode 1581B is polarized. In atleast one embodiment, the cutting member 1540 can be advanced when boththe first and second electrodes 1581A and 1581B are polarized, while, inother embodiments, the cutting member 1540 can be advanced while thesecond electrode 1581B has been polarized and after the first electrode1581A has been polarized. In various alternative embodiments, further tothe above, one of the electrodes 1581A and 1581B can be electricallycoupled with the positive terminal of the power source while the otherof the electrodes 1581A and 1581B can be electrically coupled with thenegative terminal of the power source. In at least one such embodiment,the polarity of the electrodes 1581A and 1581B can then be reversed.

In various embodiments, as described above, the end effector of asurgical instrument can comprise a first jaw member and a second jawmember, wherein the first jaw member can be rotated, or pivoted, towardthe second jaw member in order to clamp tissue between the first andsecond jaw members. In various circumstances, the first jaw member canbe pivoted between a fully open position, a fully closed position, andvarious positions inbetween. In at least one such embodiment, the firstjaw member can be pivoted from its open position into a first positionin order to apply a first clamping pressure to the tissue and, if sodesired, the first jaw member can be further pivoted into a secondposition in order to apply a second, or larger, clamping pressure to thetissue. In various circumstances, a sufficient, or certain, clampingpressure must be applied to the tissue in order for the tissue to beproperly treated by the electrical current heat supplied to, and/or heatgenerated by, the first and second jaw members via the electrodespositioned therein. In certain embodiments, a surgical instrument cancomprise means for preventing, or at least substantially preventing,current from flowing through the tissue unless the tissue is beingsubjected to a clamping pressure above a certain minimum pressure. In atleast one embodiment, one or more of the electrodes in the first andsecond jaw members can include an electrode comprising apressure-sensitive (PS) material which can have a first resistance, orimpedance, when it is subjected to pressure below the minimum pressureand a substantially higher second resistance, or impedance, when it issubjected to a pressure at and/or above the minimum pressure, asdescribed in greater detail further below.

In various embodiments, further to the above, an electrode in at leastone of the first and second jaw members can comprise apressure-sensitive material including a non-conductive, or at leastsubstantially non-conductive, substrate material and a conductivematerial dispersed within the substrate material. The pressure-sensitivematerial can be manufactured such that the conductive material ispresent within the substrate material in a certain, or predetermined,mass fraction. For example, in at least one such embodiment, thesubstrate material can be comprised of a polymeric material, such aspolyethylene and/or high-density polyethylene (HDPE), for example, andthe conductive material can be comprised of carbon black particles, forexample. In any event, when the pressure-sensitive material is not beingsubjected to external pressures, other than atmospheric pressure and/orgravity forces, for example, the pressure-sensitive material may have afirst electrical resistance, or impedance, which can make thepressure-sensitive material electrically non-conductive, or at leastsubstantially electrically non-conductive such that current cannot besufficiently conducted therethrough to either treat or irreversiblyalter the tissue captured within the end effector. In suchcircumstances, the conductive particles can be present in thepressure-sensitive material in a first volumetric density such that theconductive particles are not sufficiently in contact with another inorder to form a necessary chain, or chains, of conductive particles forelectrical current to pass therethrough. When the pressure-sensitivematerial is subjected to pressure when the clamping pressure is appliedto the tissue, for example, the conductive particles can be moved towardeach other such that they have a larger volumetric density within thepressure-sensitive material. After a sufficient, or minimum, pressurehas been applied to the pressure-sensitive material, the conductiveparticles can make sufficient contact with one another to form one ormore conductive paths though the pressure-sensitive material. Once suchconductive paths have been established, the current can flow through thepressure sensitive material and through the tissue positioned betweenthe first and second jaw members.

When the pressure-sensitive material has been sufficiently compressed inorder to conduct electrical current, further to the above, thepressure-sensitive material may have a resistance, or impedance, whichis far lower than the resistance, or impedance, of thepressure-sensitive material when it is not being compressed, forexample. In certain embodiments, as a result, the pressure-sensitivematerial may operate as a switch which switches between a first, orhigher, resistance and a second, or lower, resistance once a sufficient,or switching, pressure has been applied to the pressure-sensitivematerial. In certain embodiments, the switching pressure can beapproximately 1000 psi, approximately 1500 psi, approximately 2000 psi,and/or approximately 2500 psi, for example. In at least one embodiment,the switching pressure can be between approximately 1000 psi andapproximately 2500 psi, for example. In at least one embodiment, theminimum switching pressure can be approximately 1500 psi, for example.In certain embodiments, the switching pressure can be greater than 2500psi, for example. In various embodiments, the switching pressure of anelectrode material can be affected by moisture, the power applied,and/or time, for example. In any event, in various circumstances, thefirst resistance can be approximately 10 times larger, approximately 100times larger, and/or approximately 1000 times larger that the secondresistance, for example. In at least some such circumstances, as aresult, the pressure-sensitive material, at its first resistance, canprevent, or at least substantially inhibit, current from flowingtherethrough while the pressure-sensitive material, at its secondresistance, can permit current to flow therethrough with a sufficientmagnitude in order to treat the tissue in the end effector, for example.In various circumstances, the switching pressure can actually comprise,or be defined by, a range of pressures wherein, once the appliedpressure enters into this range, the resistance of thepressure-sensitive material can begin to decrease from the firstresistance to the second resistance as the pressure is increased. Invarious circumstances, the resistance can decrease linearly and/orgeometrically between the first resistance and the second resistance. Incertain embodiments, carbon black particles can be present in HDPE, forexample, in sufficient quantities so as to create a desired secondresistance within the electrode, such as approximately 8 ohms,approximately 100 ohms, and/or approximately 1000 ohms, for example. Invarious embodiments, the resistance of the electrode material can beinversely proportional to the density of the carbon black particleswithin the electrode material. For example, a higher density of carbonblack particles can result in a lower resistance of the electrodematerial.

In various other embodiments, an electrode can comprise apressure-sensitive material which does not comprise a distinct switchingpressure and/or distinct pressure range in which the resistance of thepressure-sensitive material changes significantly; rather, theresistance of such a pressure-sensitive material can decrease graduallyas the pressure applied to the pressure-sensitive material is increasedgradually. In various embodiments, the magnitude of the current that canflow through the pressure-resistance material can increase monotonicallyas the pressure applied to the pressure-resistance material isincreased, at least for a given voltage potential applied across thepressure-resistance material. The change in resistance can occurlinearly and/or geometrically in an inversely proportional manner to theapplied pressure. Correspondingly, the change in current, for a givenvoltage potential, can occur linearly and/or geometrically in a directlyproportional manner to the applied pressure. In such embodiments, afirst clamping pressure applied to the pressure-sensitive material canresult in the pressure-sensitive material having a first resistance, asecond clamping pressure can result in a second resistance, and a thirdclamping pressure can result in a third resistance, and so forth.

The above-discussed pressure-sensitive materials, and/or any otherpressure-sensitive materials disclosed herein, can be formed utilizingany suitable manufacturing process. In various embodiments, thepressure-sensitive material, including those comprised of a polymericsubstrate, for example, can be formed utilizing an injection moldingprocess. In at least one such embodiment, polyethylene can be heateduntil its melting temperature has been reached and/or exceeded. Before,during and/or after this heating process, carbon black particles can bemixed into the polyethylene wherein the heated mixture can be stirreduntil the mixture is homogeneous, or at least substantially homogeneous.Thereafter, the mixture can be injected into one or more cavities of amold such that the mixture can then cool below the melting temperatureof the polyethylene material and take the shape of the mold cavity. Oncethe mixture has been sufficiently cooled, the mold can be opened and themolded pressure-sensitive material can be removed from the cavity. Invarious circumstances, the pressure-sensitive material can then beexposed to gamma radiation which can at least partially crystallize thepolyethylene. In various embodiments, the material can be exposed to twodoses of approximately 15-20 kGy each, for example, resulting inapproximately 40 kGy maximum total exposure, for example. In variouscircumstances, the gamma radiation process can cause the carbon blackparticles to migrate and accumulate in pockets intermediate thecrystallized portions of the polyethylene. In various embodiments, thecarbon black particles can comprise an average diameter of approximately10 microns, for example, and can comprise any suitable geometry and/orconfiguration such as bucky balls and/or tubular ferrules, for example.In any event, in the event that the electrodes comprising suchpressure-sensitive materials are to be sterilized, it may be desirableto avoid sterilizing the electrodes using gamma radiation as doing somay affect the performance characteristics of the pressure-sensitivematerials in some circumstances. Other sterilization processes, such asthose utilizing ethylene oxide, for example, could be used.

In various embodiments, referring now to FIGS. 34-37, a surgicalinstrument can comprise one or more electrodes utilizing both apressure-sensitive (PS) material and a positive temperature coefficient(PTC) material. Referring primarily to FIG. 34, an electrode 2365 cancomprise a first, or top, layer 2301 comprising a PTC material and asecond, or bottom, layer 2302 comprising a PS material. In variousembodiments, similar to the above, the PTC material of the first layer2301 can comprise a non-conductive, or at least substantiallynon-conductive, substrate 2304 and conductive particles 2305 dispersedtherein. Also similar to the above, the PS material of the second layer2302 can comprise a non-conductive, or at least substantiallynon-conductive, substrate 2306 and conductive particles 2307 dispersedtherein. The electrode 2365 can further comprise a support, or bottom,surface 2308 configured to support the electrode 2365 within a jawmember of an electrosurgical instrument, for example, wherein, incertain embodiments, the electrode 2365 can further comprise aconductive sheet attached to bottom surface 2308. In at least one suchembodiment, the conductive sheet can be adhered to the bottom surface2308 utilizing an adhesive while, in other embodiments, the conductivesheet may be unattached to the electrode 2365 and the bottom surface2308 may abut the conductive sheet. In any event, a conductor, such asan insulated wire, for example, may be electrically coupled with theconductive sheet such that a voltage potential can be applied to thebottom surface 2308 of the electrode 2365. On the opposite side of theelectrode 2365, the electrode 2365 can further comprise atissue-contacting surface 2303 which can be configured to contact tissuepositioned between a jaw including electrode 2365 and an opposing jawpositioned on the opposite side of the tissue. In at least one suchembodiment, the opposing jaw can comprise an electrode 2365 positionedin a mirror-image arrangement such that the tissue-contacting surfaces2303 of the electrodes 2365 face one another.

In various embodiments, further to the above, the first layer 2301 cancomprise means for controlling and/or evaluating the temperature of thetissue and, in addition, the second layer 2302 can comprise means forassuring that the current cannot flow through the electrode 2365 untilthe tissue being treated by the electrode 2365 is positioned againsttissue-contacting surface 2303 with sufficient pressure. In at least onesuch embodiment, the PTC material of layer 2301 can comprise a thermalswitch and the PS material of layer 2302 can comprise a pressure switchwhich can be configured to co-operate with one another in order toassure that temperature of the tissue being treated does not exceed acertain temperature and such that the tissue being treated is beingsufficiently compressed. Referring again to FIG. 34, the PTC material offirst layer 2301 is illustrated as being below its switching temperatureTs and, as a result, the conductive particles 2305 in substrate 2304 aresufficiently in contact with one another in order for current to beconducted through the first layer 2301. The PS material of second layer2302, however, is illustrated in FIG. 34 as being below its switchingpressure Ps and, as a result, the conductive particles 2307 in substrate2306 are not sufficiently in contact with one another in order forcurrent to be conducted through layer 2302, at least not in a magnitudesufficient to generate therapeutic and/or irreversible effects withinthe tissue positioned against tissue-contacting surface 2303. In suchcircumstances, as a result, the resistance between surfaces 2303 and2308 is too large for a sufficient current, if any, to be transmittedbetween the surfaces 2303 and 2308 in order to treat the tissue, atleast for the voltage potential applied to the bottom surface 2308, forexample.

Referring again to FIG. 34, the reader will note that the substrate 2304of first layer 2301 is illustrated as being shaded-in, or darkened,while the substrate 2306 of second layer 2302 is illustrated as notbeing shaded-in. This has been done in order to schematicallyillustrate, by way of example, that the darkened first layer 2301comprises a “closed” portion of the series circuit between surfaces 2303and 2308 and that the non-darkened second layer 2302 comprises an “open”portion of the series circuit. In various circumstances, the term“closed” can designate that current could flow through that portion ofthe circuit with a sufficient amplitude in order to therapeuticallytreat, and/or irreversibly affect, the tissue, whereas the term “open”can designate that current cannot flow through that portion of thecircuit with a sufficient amplitude to therapeutically treat, and/orirreversibly affect, the tissue. In certain circumstances, the term“open” can designate that the current can flow through that portion ofthe circuit at all. In various circumstances, if one or both layers 2301and 2302 represent an open part of the circuit between surfaces 2303 and2308, the entire circuit between surfaces 2303 and 2308 will, as aresult, be open. In circumstances where both layers 2301 and 2302 areclosed, the entire series circuit between surfaces 2303 and 2308 will beclosed and sufficient therapeutic current can flow therethrough.

Referring now to FIG. 35, further to the above, the PTC material of thefirst layer 2301 is illustrated as being below its switching temperatureTs and, as a result, the conductive particles 2305 in substrate 2304 aresufficiently in contact with one another in order for current to beconducted through the first layer 2301. As the reader will note,substrate 2304 is correspondingly illustrated as being shaded-in ordarkened as it is in a “closed” condition. Still referring to FIG. 35,the PS material of second layer 2302 is illustrated as being above itsswitching pressure Ps and, as a result, the conductive particles 2307 insubstrate 2306 are sufficiently in contact with one another in order forcurrent to be conducted through the second layer 2302. As the readerwill note, substrate 2306 is illustrated as being shaded-in or darkenedas it is also in a “closed” condition. As a result of the above, theseries circuit between surfaces 2303 and 2308 is in a “closed” conditionand, accordingly, sufficiently therapeutic current can flow throughbetween surfaces 2303 and 2308 of the electrode 2365. The state of theelectrode 2365 in FIG. 35 can represent the condition in which theelectrosurgical instrument comprising the electrode 2365 has capturedand clamped tissue within the end effector and can be utilized to treatthe tissue. In various embodiments, a voltage potential betweenapproximately 60 V and approximately 105 V, for example, can be appliedto the electrode 2365 in order to treat the tissue. In at least oneembodiment, a voltage potential of approximately 85 V, for example, canbe applied to the electrode 2365. In certain embodiments, a maximumvoltage potential, such as 105 V, for example, can be set in order toreduce the possibility of the electrode material breaking down andcreating a short within the electrode material, for example.

Referring now to FIG. 36, the PTC material of the first layer 2301 isillustrated as being above its switching temperature Ts and, as aresult, the conductive particles 2305 in substrate 2304 are notsufficiently in contact with one another in order for current to beconducted through layer 2301, at least not in a magnitude sufficient togenerate therapeutic and/or irreversible effects within the tissuepositioned against tissue-contacting surface 2303. As the reader willnote, substrate 2304 is correspondingly illustrated as beingnon-darkened as it is in an “open” condition. Accordingly, the seriescircuit between surfaces 2303 and 2308 is in an “open” conditioneventhough the pressure applied to electrode 2365 is above the switchingpressure Ps and the second layer 2302 is in a “closed” configuration.Referring now to FIG. 37, the PTC material of the first layer 2301 isillustrated as being above its switching temperature Ts and the secondlayer 2302 is illustrated as being below its switching pressure Ps. As aresult, both layers 2301 and 2302 are “open” and are illustrated asbeing non-darkened. Accordingly, the series circuit between surfaces2303 and 2308 is in an “open” condition. In various alternativeembodiments, one or both of the first and second layers 2301 and 2302may not act as switches; rather, one or both of the layers 2301 and 2302may provide variable resistances depending on the temperature andpressure, respectively, being applied to the tissue. More particularly,in at least one embodiment, the PTC and/or PS materials may not switchbetween open and closed conditions; rather, the electrical resistancesof the materials may change linearly and/or geometrically in amonotonical manner, wherein the resistance of the PTC material of thefirst layer 2301 may increase as the temperature of the tissueincreases, and wherein the resistance of the PS material of the secondlayer 2302 may decrease as the pressure applied to the tissue increases.

In various embodiments, further to the above, the first layer 2301 canbe stacked on top of the second layer 2302 such that they have abuttingfaces at interface 2309. In certain embodiments, the first layer 2301can be adhered to the second layer 2302. In at least one embodiment, thefirst layer 2301 and the second layer 2302 can be co-extruded such thatthey form a bonded interface therebetween. In at least one suchembodiment, the PTC material comprising the first layer 2301 can bepositioned on top of the PS material comprising the second layer 2302such that the assembled materials can be fed through a die and, as aresult of pressure and/or temperature being applied to the PTC and PSmaterials, the layers 2301 and 2302 can form at least one of amechanical bond and a chemical bond therebetween. Stated another way,the layers 2301 and 2302 can be co-extruded.

As discussed above, a pressure-sensitive (PS) material can eitherprevent and/or limit the flow of current passing therethrough as afunction of the pressure being applied to the PS material. In at leastone such embodiment, as also described above, the PS material cancomprise a pressure switch which change between a high electricalresistance and a low electrical resistance depending on whether theapplied pressure is below or above, respectively, the switching pressurePs. In various embodiments, a PS material can also comprise certaincharacteristics of a positive temperature coefficient (PTC) material.More particularly, in at least one embodiment, once a sufficientpressure has been applied to the PS material and the conductiveparticles within the substrate of the PS material have been sufficientlysqueezed together such that the PS material is capable of conductingtherapeutic current therethrough, such current can cause the PS materialto increase in temperature. Owing to the increase in temperature, the PSmaterial substrate can begin to expand and/or change state such that theconductive particles are no longer in contact with each other, or atleast sufficiently in contact with one another, in order to conduct atherapeutic current therethrough. In various circumstances, as a result,the PS material can also act as a temperature switch wherein, in atleast one embodiment, the PS material can go through three states: afirst state which is “open” owing to the pressure switchingcharacteristics of the material, a second state which is “closed”, and athird state which is “open” owing to the temperature switchingcharacteristics of the material. More particularly, the material canhave a first state having a first resistance which is sufficiently highto prevent or inhibit current from flowing therethrough before theswitching pressure is applied, a second state having a second resistancewhich is sufficiently low to allow a therapeutic current to flowtherethrough, and a third state having a third resistance which issufficiently high to prevent or inhibit current from flowingtherethrough because the switching temperature has been exceeded, forexample.

The embodiments of the devices described herein may be introduced insidea patient using minimally invasive or open surgical techniques. In someinstances it may be advantageous to introduce the devices inside thepatient using a combination of minimally invasive and open surgicaltechniques. Minimally invasive techniques may provide more accurate andeffective access to the treatment region for diagnostic and treatmentprocedures. To reach internal treatment regions within the patient, thedevices described herein may be inserted through natural openings of thebody such as the mouth, anus, and/or vagina, for example. Minimallyinvasive procedures performed by the introduction of various medicaldevices into the patient through a natural opening of the patient areknown in the art as NOTES™ procedures. Some portions of the devices maybe introduced to the tissue treatment region percutaneously or throughsmall—keyhole—incisions.

Endoscopic minimally invasive surgical and diagnostic medical proceduresare used to evaluate and treat internal organs by inserting a small tubeinto the body. The endoscope may have a rigid or a flexible tube. Aflexible endoscope may be introduced either through a natural bodyopening (e.g., mouth, anus, and/or vagina) or via a trocar through arelatively small—keyhole—incision incisions (usually 0.5-1.5 cm). Theendoscope can be used to observe surface conditions of internal organs,including abnormal or diseased tissue such as lesions and other surfaceconditions and capture images for visual inspection and photography. Theendoscope may be adapted and configured with working channels forintroducing medical instruments to the treatment region for takingbiopsies, retrieving foreign objects, and/or performing surgicalprocedures.

The devices disclosed herein may be designed to be disposed of after asingle use, or they may be designed to be used multiple times. In eithercase, however, the device may be reconditioned for reuse after at leastone use. Reconditioning may include a combination of the steps ofdisassembly of the device, followed by cleaning or replacement ofparticular pieces, and subsequent reassembly. In particular, the devicemay be disassembled, and any number of particular pieces or parts of thedevice may be selectively replaced or removed in any combination. Uponcleaning and/or replacement of particular parts, the device may bereassembled for subsequent use either at a reconditioning facility, orby a surgical team immediately prior to a surgical procedure. Those ofordinary skill in the art will appreciate that the reconditioning of adevice may utilize a variety of different techniques for disassembly,cleaning/replacement, and reassembly. Use of such techniques, and theresulting reconditioned device, are all within the scope of thisapplication.

Preferably, the various embodiments of the devices described herein willbe processed before surgery. First, a new or used instrument is obtainedand if necessary cleaned. The instrument can then be sterilized. In onesterilization technique, the instrument is placed in a closed and sealedcontainer, such as a plastic or TYVEK® bag. The container and instrumentare then placed in a field of radiation that can penetrate thecontainer, such as gamma radiation, x-rays, or high-energy electrons.The radiation kills bacteria on the instrument and in the container. Thesterilized instrument can then be stored in the sterile container. Thesealed container keeps the instrument sterile until it is opened in themedical facility. Other sterilization techniques can be done by anynumber of ways known to those skilled in the art including beta or gammaradiation, ethylene oxide, and/or steam.

It will be appreciated that the terms “proximal” and “distal” may beused throughout the specification with reference to a clinicianmanipulating one end of an instrument used to treat a patient. The term“proximal” refers to the portion of the instrument closest to theclinician and the term “distal” refers to the portion located furthestfrom the clinician. It will be further appreciated that for concisenessand clarity, spatial terms such as “vertical,” “horizontal,” “up,” and“down” may be used herein with respect to the illustrated embodiments.However, surgical instruments may be used in many orientations andpositions, and these terms are not intended to be limiting and absolute.

Although the various embodiments of the devices have been describedherein in connection with certain disclosed embodiments, manymodifications and variations to those embodiments may be implemented.For example, different types of end effectors may be employed. Also,where materials are disclosed for certain components, other materialsmay be used. Furthermore, according to various embodiments, a singlecomponent may be replaced by multiple components, and multiplecomponents may be replaced by a single component, to perform a givenfunction or functions. The foregoing description and following claimsare intended to cover all such modification and variations.

Any patent, publication, or other disclosure material, in whole or inpart, that is said to be incorporated by reference herein isincorporated herein only to the extent that the incorporated materialsdoes not conflict with existing definitions, statements, or otherdisclosure material set forth in this disclosure. As such, and to theextent necessary, the disclosure as explicitly set forth hereinsupersedes any conflicting material incorporated herein by reference.Any material, or portion thereof, that is said to be incorporated byreference herein, but which conflicts with existing definitions,statements, or other disclosure material set forth herein will only beincorporated to the extent that no conflict arises between thatincorporated material and the existing disclosure material.

1. A surgical instrument, comprising: a handle; a first conductor; asecond conductor; and an end effector, comprising: a first jaw; a secondjaw, wherein one of said first jaw and said second jaw is movablerelative to the other of said first jaw and said second jaw between anopen position and a closed position; a first electrode electricallycoupled with said first conductor; and a second electrode electricallycoupled with said second conductor, said second electrode comprising: aporous material; and an evaporable material stored within said porousmaterial.
 2. The surgical instrument of claim 1, wherein said evaporablematerial is electrically conductive and said porous material iselectrically non-conductive.
 3. The surgical instrument of claim 1,wherein said evaporable material has a boiling point of approximately100 degrees Celsius at approximately 1 atm atmospheric pressure.
 4. Thesurgical instrument of claim 1, wherein said evaporable materialcomprises isotonic saline.
 5. The surgical instrument of claim 1,wherein said porous material comprises a first side and a second side,wherein said second electrode further comprises: a first conductivesurface positioned on said first side of said porous material, whereinsaid second conductor is electrically coupled with said first conductivesurface; and a conductive tissue-contacting surface conductive surfacepositioned on said second side of said porous material.
 6. The surgicalinstrument of claim 1, wherein said second electrode further comprises asealed enclosure, and wherein said porous material and said evaporablematerial are positioned within said sealed enclosure.
 7. The surgicalinstrument of claim 1, wherein said first electrode is positioned insaid first jaw, and wherein said second electrode is positioned in saidsecond jaw.
 8. The surgical instrument of claim 1, wherein saidevaporable material comprises a first evaporable material, wherein saidsecond electrode further comprises a second evaporable material storedwithin said porous material, and wherein said first evaporable materialcomprises a boiling point temperature which is less than a boiling pointtemperature of said second material.
 9. A surgical instrument,comprising: a handle; a first conductor; a second conductor electricallyengageable with a power source; and an end effector, comprising: a firstjaw; a second jaw, wherein one of said first jaw and said second jaw ismovable relative to the other of said first jaw and said second jawbetween an open position and a closed position; a first electrodeelectrically coupled with said first conductor; and a second electrodeelectrically coupled with said second conductor, said second electrodecomprising: a first material comprised of an electrically non-conductivematerial; and a second material comprised of an electrically conductivematerial, wherein said second material is interdispersed within saidfirst material when said second electrode is below a switchingtemperature, and wherein said second material is configured to withdrawfrom said first material when the temperature of said second material atleast one of meets or exceeds said switching temperature.
 10. Thesurgical instrument of claim 9, wherein said switching temperaturecomprises a boiling point temperature of said second material, andwherein said second material can evaporate from said first material whenthe temperature of said second material is at said boiling pointtemperature.
 11. The surgical instrument of claim 10, wherein saidboiling point is approximately 100 degrees Celsius at approximately 1atm atmospheric pressure.
 12. The surgical instrument of claim 10,wherein said second electrode further comprises a sealed enclosure, andwherein said first material and said second material are positionedwithin said sealed enclosure.
 13. The surgical instrument of claim 9,wherein said second material comprises isotonic saline.
 14. The surgicalinstrument of claim 9, wherein said first material comprises a firstside and a second side, wherein said second electrode further comprises:a first conductive surface positioned on said first side of said firstmaterial, wherein said second conductor is electrically coupled withsaid first conductive surface; and a conductive tissue-contactingsurface conductive surface positioned on said second side of said firstmaterial.
 15. The surgical instrument of claim 9, wherein said firstelectrode is positioned in said first jaw, and wherein said secondelectrode is positioned in said second jaw.
 16. An end effector for usewith a surgical instrument, comprising: a first conductor; a secondconductor; a first jaw; a second jaw, wherein one of said first jaw andsaid second jaw is movable relative to the other of said first jaw andsaid second jaw between an open position and a closed position; a firstelectrode electrically coupled with said first conductor; and a secondelectrode electrically coupled with said second conductor, said secondelectrode comprising: a porous material; and an evaporable materialstored within said porous material.
 17. The surgical instrument of claim16, wherein said evaporable material is electrically conductive and saidporous material is electrically non-conductive.
 18. The surgicalinstrument of claim 16, wherein said evaporable material has a boilingpoint of approximately 100 degrees Celsius at approximately 1 atmatmospheric pressure.
 19. The surgical instrument of claim 16, whereinsaid evaporable material comprises isotonic saline.
 20. A surgicalinstrument, comprising: a first jaw comprising an electrode; a secondjaw; a control circuit, comprising: a supply conductor configured to beplaced in electrical communication with a positive terminal of a powersource; a temperature sensor; and a field effect transistor, comprising:a source terminal in electrical communication with said supplyconductor; a drain terminal in electrical communication with saidelectrode; and a gate terminal in electrical communication with saidtemperature sensor; and a channel comprising a semiconductor material inelectrical communication with said source terminal and said drainterminal.